[PATCH v2 0/8] Fix TPM 2.0 trusted keys

[PATCH v2 0/8] Fix TPM 2.0 trusted keys

[James Bottomley]

This fixes a wide array of problems with the current TPM 2.0
implementation of trusted keys.  Since policy based trusted keys never
worked in the current implementation, I've rewritten the policy
implementation to make it easier to use and so the trusted key handler
can understand what elements of a policy are failing and why.

Apart from fixing bugs like volatile object leakage, I've changed the
output format to use the standardised ASN.1 coding for TPM2 keys,
meaning they should interoperate with userspace TPM2 key
implementations.  Apart from interoperability, another advantage of the
existing key format is that it carries all parameters like parent and
hash with it and it is capable of carrying policy directives in a way
that mean they're tied permanently to the key (no having to try to
remember what the policy was and reconstruct it from userspace).  This
actually allows us to support the TPM 1.2 commands like pcrinfo easily
in 2.0.

The big problem with this patch is still that we can't yet combine
policy with authorization because that requires proper session
handling, but at least with this rewrite it becomes possible (whereas
it was never possible with the old external policy session code). 
Thus, when we have the TPM 2.0 security patch upstream, we'll be able
to use the session logic from that patch to imlement authorizations.

James

---

v2: Fix all the code review issues noticed by David Woodhouse and redo
    the ASN.1 encoder API to allow in-place encoding for short tags
    and sequences


James Bottomley (8):
  security: keys: trusted: flush the key handle after use
  lib: add asn.1 encoder
  oid_registry: Add TCG defined OIDS for TPM keys
  security: keys: trusted: use ASN.1 tpm2 key format for the blobs
  security: keys: trusted: Make sealed key properly interoperable
  security: keys: trusted: add PCR policy to TPM2 keys
  security: keys: trusted: add ability to specify arbitrary policy
  security: keys: trusted: implement counter/timer policy

 Documentation/security/keys/trusted-encrypted.rst |  70 +++-
 drivers/char/tpm/tpm.h                            |   1 -
 drivers/char/tpm/tpm2-cmd.c                       |   1 +
 include/keys/trusted-type.h                       |   6 +-
 include/linux/asn1_encoder.h                      |  21 ++
 include/linux/oid_registry.h                      |   5 +
 include/linux/tpm.h                               |   8 +
 lib/Makefile                                      |   2 +-
 lib/asn1_encoder.c                                | 258 ++++++++++++++
 security/keys/Kconfig                             |   2 +
 security/keys/trusted-keys/Makefile               |   2 +-
 security/keys/trusted-keys/tpm2-policy.c          | 405 ++++++++++++++++++++++
 security/keys/trusted-keys/tpm2-policy.h          |  31 ++
 security/keys/trusted-keys/tpm2key.asn1           |  23 ++
 security/keys/trusted-keys/trusted_tpm1.c         |  40 +--
 security/keys/trusted-keys/trusted_tpm2.c         | 307 ++++++++++++++--
 16 files changed, 1124 insertions(+), 58 deletions(-)
 create mode 100644 include/linux/asn1_encoder.h
 create mode 100644 lib/asn1_encoder.c
 create mode 100644 security/keys/trusted-keys/tpm2-policy.c
 create mode 100644 security/keys/trusted-keys/tpm2-policy.h
 create mode 100644 security/keys/trusted-keys/tpm2key.asn1

-- 
2.16.4

[PATCH v2 0/8] Fix TPM 2.0 trusted keys

[James Bottomley]

This fixes a wide array of problems with the current TPM 2.0
implementation of trusted keys.  Since policy based trusted keys never
worked in the current implementation, I've rewritten the policy
implementation to make it easier to use and so the trusted key handler
can understand what elements of a policy are failing and why.

Apart from fixing bugs like volatile object leakage, I've changed the
output format to use the standardised ASN.1 coding for TPM2 keys,
meaning they should interoperate with userspace TPM2 key
implementations.  Apart from interoperability, another advantage of the
existing key format is that it carries all parameters like parent and
hash with it and it is capable of carrying policy directives in a way
that mean they're tied permanently to the key (no having to try to
remember what the policy was and reconstruct it from userspace).  This
actually allows us to support the TPM 1.2 commands like pcrinfo easily
in 2.0.

The big problem with this patch is still that we can't yet combine
policy with authorization because that requires proper session
handling, but at least with this rewrite it becomes possible (whereas
it was never possible with the old external policy session code). 
Thus, when we have the TPM 2.0 security patch upstream, we'll be able
to use the session logic from that patch to imlement authorizations.

James

---

v2: Fix all the code review issues noticed by David Woodhouse and redo
    the ASN.1 encoder API to allow in-place encoding for short tags
    and sequences


James Bottomley (8):
  security: keys: trusted: flush the key handle after use
  lib: add asn.1 encoder
  oid_registry: Add TCG defined OIDS for TPM keys
  security: keys: trusted: use ASN.1 tpm2 key format for the blobs
  security: keys: trusted: Make sealed key properly interoperable
  security: keys: trusted: add PCR policy to TPM2 keys
  security: keys: trusted: add ability to specify arbitrary policy
  security: keys: trusted: implement counter/timer policy

 Documentation/security/keys/trusted-encrypted.rst |  70 +++-
 drivers/char/tpm/tpm.h                            |   1 -
 drivers/char/tpm/tpm2-cmd.c                       |   1 +
 include/keys/trusted-type.h                       |   6 +-
 include/linux/asn1_encoder.h                      |  21 ++
 include/linux/oid_registry.h                      |   5 +
 include/linux/tpm.h                               |   8 +
 lib/Makefile                                      |   2 +-
 lib/asn1_encoder.c                                | 258 ++++++++++++++
 security/keys/Kconfig                             |   2 +
 security/keys/trusted-keys/Makefile               |   2 +-
 security/keys/trusted-keys/tpm2-policy.c          | 405 ++++++++++++++++++++++
 security/keys/trusted-keys/tpm2-policy.h          |  31 ++
 security/keys/trusted-keys/tpm2key.asn1           |  23 ++
 security/keys/trusted-keys/trusted_tpm1.c         |  40 +--
 security/keys/trusted-keys/trusted_tpm2.c         | 307 ++++++++++++++--
 16 files changed, 1124 insertions(+), 58 deletions(-)
 create mode 100644 include/linux/asn1_encoder.h
 create mode 100644 lib/asn1_encoder.c
 create mode 100644 security/keys/trusted-keys/tpm2-policy.c
 create mode 100644 security/keys/trusted-keys/tpm2-policy.h
 create mode 100644 security/keys/trusted-keys/tpm2key.asn1

-- 
2.16.4

[PATCH v2 1/8] security: keys: trusted: flush the key handle after use

[James Bottomley]

The trusted keys code currently loads a blob into the TPM and unseals
on the handle.  However, it never flushes the handle meaning that
volatile contexts build up until the TPM becomes unusable.  Fix this
by flushing the handle after the unseal.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: use EXPORT_SYMBOL_GPL
---
 drivers/char/tpm/tpm.h                    | 1 -
 drivers/char/tpm/tpm2-cmd.c               | 1 +
 include/linux/tpm.h                       | 1 +
 security/keys/trusted-keys/trusted_tpm2.c | 1 +
 4 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index b9e1547be6b5..5620747da0cf 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -218,7 +218,6 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
 int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 		    struct tpm_digest *digests);
 int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
-void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
 ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,
 			u32 *value, const char *desc);
 
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index fdb457704aa7..13696deceae8 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -362,6 +362,7 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
 	tpm_transmit_cmd(chip, &buf, 0, "flushing context");
 	tpm_buf_destroy(&buf);
 }
+EXPORT_SYMBOL_GPL(tpm2_flush_context);
 
 struct tpm2_get_cap_out {
 	u8 more_data;
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 0d6e949ba315..03e9b184411b 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -403,6 +403,7 @@ extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen);
 extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
 extern struct tpm_chip *tpm_default_chip(void);
+void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
 #else
 static inline int tpm_is_tpm2(struct tpm_chip *chip)
 {
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index a9810ac2776f..08ec7f48f01d 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -309,6 +309,7 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
 		return rc;
 
 	rc = tpm2_unseal_cmd(chip, payload, options, blob_handle);
+	tpm2_flush_context(chip, blob_handle);
 
 	return rc;
 }
-- 
2.16.4

[PATCH v2 1/8] security: keys: trusted: flush the key handle after use

[James Bottomley]

The trusted keys code currently loads a blob into the TPM and unseals
on the handle.  However, it never flushes the handle meaning that
volatile contexts build up until the TPM becomes unusable.  Fix this
by flushing the handle after the unseal.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: use EXPORT_SYMBOL_GPL
---
 drivers/char/tpm/tpm.h                    | 1 -
 drivers/char/tpm/tpm2-cmd.c               | 1 +
 include/linux/tpm.h                       | 1 +
 security/keys/trusted-keys/trusted_tpm2.c | 1 +
 4 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index b9e1547be6b5..5620747da0cf 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -218,7 +218,6 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
 int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 		    struct tpm_digest *digests);
 int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
-void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
 ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,
 			u32 *value, const char *desc);
 
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index fdb457704aa7..13696deceae8 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -362,6 +362,7 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
 	tpm_transmit_cmd(chip, &buf, 0, "flushing context");
 	tpm_buf_destroy(&buf);
 }
+EXPORT_SYMBOL_GPL(tpm2_flush_context);
 
 struct tpm2_get_cap_out {
 	u8 more_data;
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 0d6e949ba315..03e9b184411b 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -403,6 +403,7 @@ extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen);
 extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
 extern struct tpm_chip *tpm_default_chip(void);
+void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
 #else
 static inline int tpm_is_tpm2(struct tpm_chip *chip)
 {
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index a9810ac2776f..08ec7f48f01d 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -309,6 +309,7 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
 		return rc;
 
 	rc = tpm2_unseal_cmd(chip, payload, options, blob_handle);
+	tpm2_flush_context(chip, blob_handle);
 
 	return rc;
 }
-- 
2.16.4

[PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

We have a need in the TPM trusted keys to return the ASN.1 form of the
TPM key blob so it can be operated on by tools outside of the kernel.
To do that, we have to be able to read and write the key format.  The
current ASN.1 decoder does fine for reading, but we need pieces of an
ASN.1 encoder to return the key blob.

The current implementation only encodes the ASN.1 bits we actually need.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: updated API to use indefinite length, and made symbol exports gpl
---
 include/linux/asn1_encoder.h |  21 ++++
 lib/Makefile                 |   2 +-
 lib/asn1_encoder.c           | 258 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 280 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/asn1_encoder.h
 create mode 100644 lib/asn1_encoder.c

diff --git a/include/linux/asn1_encoder.h b/include/linux/asn1_encoder.h
new file mode 100644
index 000000000000..9cfb8035dc46
--- /dev/null
+++ b/include/linux/asn1_encoder.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _LINUX_ASN1_ENCODER_H
+#define _LINUX_ASN1_ENCODER_H
+
+#include <linux/types.h>
+#include <linux/asn1.h>
+#include <linux/asn1_ber_bytecode.h>
+
+#define asn1_oid_len(oid) (sizeof(oid)/sizeof(u32))
+void asn1_encode_integer(unsigned char **_data, s64 integer, int len);
+void asn1_encode_oid(unsigned char **_data, u32 oid[], int oid_len);
+void asn1_encode_tag(unsigned char **data, u32 tag,
+		     const unsigned char *string, int len);
+void asn1_encode_octet_string(unsigned char **data, const unsigned char *string,
+			      u32 len);
+void asn1_encode_sequence(unsigned char **data, const unsigned char *seq,
+			  int len);
+void asn1_encode_boolean(unsigned char **data, bool val);
+
+#endif
diff --git a/lib/Makefile b/lib/Makefile
index c2f0e2a4e4e8..515b35f92c3c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -233,7 +233,7 @@ obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o
 
 obj-$(CONFIG_PERCPU_TEST) += percpu_test.o
 
-obj-$(CONFIG_ASN1) += asn1_decoder.o
+obj-$(CONFIG_ASN1) += asn1_decoder.o asn1_encoder.o
 
 obj-$(CONFIG_FONT_SUPPORT) += fonts/
 
diff --git a/lib/asn1_encoder.c b/lib/asn1_encoder.c
new file mode 100644
index 000000000000..768cabf8bf76
--- /dev/null
+++ b/lib/asn1_encoder.c
@@ -0,0 +1,258 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Simple encoder primitives for ASN.1 BER/DER/CER
+ *
+ * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
+ */
+
+#include <linux/asn1_encoder.h>
+#include <linux/bug.h>
+#include <linux/string.h>
+#include <linux/module.h>
+
+/**
+ * asn1_encode_integer - encode positive integer to ASN.1
+ * @_data: pointer to the pointer to the data
+ * @integer: integer to be encoded
+ * @len: length of buffer
+ *
+ * This is a simplified encoder: it only currently does
+ * positive integers, but it should be simple enough to add the 
+ * negative case if a use comes along.
+ */
+void asn1_encode_integer(unsigned char **_data, s64 integer, int len)
+{
+	unsigned char *data = *_data, *d = &data[2];
+	int i;
+	bool found = false;
+
+	if (WARN(integer < 0,
+		 "BUG: asn1_encode_integer only supports positive integers"))
+		return;
+
+	if (WARN(len < 3,
+		 "BUG: buffer for integers must have at least 3 bytes"))
+		return;
+
+	len =- 2;
+
+	data[0] = _tag(UNIV, PRIM, INT);
+	if (integer = 0) {
+		*d++ = 0;
+		goto out;
+	}
+	for (i = sizeof(integer); i > 0 ; i--) {
+		int byte = integer >> (8*(i-1));
+
+		if (!found && byte = 0)
+			continue;
+		found = true;
+		if (byte & 0x80) {
+			/*
+			 * no check needed here, we already know we
+			 * have len >= 1
+			 */
+			*d++ = 0;
+			len--;
+		}
+		if (WARN(len = 0,
+			 "BUG buffer too short in asn1_encode_integer"))
+			return;
+		*d++ = byte;
+		len--;
+	}
+ out:
+	data[1] = d - data - 2;
+	*_data = d;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_integer);
+
+/* calculate the base 128 digit values setting the top bit of the first octet */
+static void asn1_encode_oid_digit(unsigned char **_data, u32 oid)
+{
+	int start = 7 + 7 + 7 + 7;
+	unsigned char *data = *_data;
+
+	/* quick case */
+	if (oid = 0) {
+		*data++ = 0x80;
+		goto out;
+	}
+
+	while (oid >> start = 0)
+		start -= 7;
+
+	while (start > 0) {
+		u8 byte;
+
+		byte = oid >> start;
+		oid = oid - (byte << start);
+		start -= 7;
+		byte |= 0x80;
+		*data++ = byte;
+	}
+	*data++ = oid;
+
+ out:
+	*_data = data;
+}
+
+/**
+ * asn1_encode_oid - encode an oid to ASN.1
+ * @_data: position to begin encoding at
+ * @oid: array of oids
+ * @oid_len: length of oid array
+ *
+ * this encodes an OID up to ASN.1 when presented as an array of OID values
+ */
+void asn1_encode_oid(unsigned char **_data, u32 oid[], int oid_len)
+{
+	unsigned char *data = *_data;
+	unsigned char *d = data + 2;
+	int i;
+
+	if (WARN(oid_len < 2, "OID must have at least two elements"))
+		return;
+	if (WARN(oid_len > 32, "OID is too large"))
+		return;
+
+	data[0] = _tag(UNIV, PRIM, OID);
+	*d++ = oid[0] * 40 + oid[1];
+	for (i = 2; i < oid_len; i++)
+		asn1_encode_oid_digit(&d, oid[i]);
+	data[1] = d - data - 2;
+	*_data = d;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_oid);
+
+static void asn1_encode_length(unsigned char **data, int len)
+{
+	if (len < 0) {
+		*((*data)++) = ASN1_INDEFINITE_LENGTH;
+		return;
+	}
+	if (len <= 0x7f) {
+		*((*data)++) = len;
+		return;
+	}
+	if (len <= 0xff) {
+		*((*data)++) = 0x81;
+		*((*data)++) = len & 0xff;
+		return;
+	}
+	if (len <= 0xffff) {
+		*((*data)++) = 0x82;
+		*((*data)++) = (len >> 8) & 0xff;
+		*((*data)++) = len & 0xff;
+		return;
+	}
+
+	if (WARN(len > 0xffffff, "ASN.1 length can't be > 0xffffff"))
+		return;
+
+	*((*data)++) = 0x83;
+	*((*data)++) = (len >> 16) & 0xff;
+	*((*data)++) = (len >> 8) & 0xff;
+	*((*data)++) = len & 0xff;
+}
+
+/**
+ * asn1_encode_tag - add a tag for optional or explicit value
+ * @data: pointer to place tag at
+ * @tag: tag to be placed
+ * @string: the data to be tagged
+ * @len: the length of the data to be tagged
+ *
+ * Note this currently only handles short form tags < 31.  To encode
+ * in place pass a NULL @string and -1 for @len; all this will do is
+ * add an indefinite length tag and update the data pointer to the
+ * place where the tag contents should be placed.  After the data is
+ * placed, repeat the prior statement but now with the known length.
+ * In order to avoid having to keep both before and after pointers,
+ * the repeat expects to be called with @data pointing to where the
+ * first encode placed it.
+ */
+void asn1_encode_tag(unsigned char **data, u32 tag,
+		     const unsigned char *string, int len)
+{
+	if (WARN(tag > 30, "ASN.1 tag can't be > 30"))
+		return;
+
+	if (!string && WARN(len > 127,
+			    "BUG: recode tag is too big (>127)"))
+		return;
+
+	if (!string && len > 0)
+		/* we're recoding, so move back to the start of the tag */
+		*data -= 2;
+
+	*((*data)++) = _tagn(CONT, CONS, tag);
+	asn1_encode_length(data, len);
+	if (!string)
+		return;
+	memcpy(*data, string, len);
+	*data += len;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_tag);
+
+/**
+ * asn1_encode_octet_string - encode an ASN.1 OCTET STRING
+ * @data: pointer to encode at
+ * @string: string to be encoded
+ * @len: length of string
+ *
+ * Note ASN.1 octet strings may contain zeros, so the length is obligatory.
+ */
+void asn1_encode_octet_string(unsigned char **data, const unsigned char *string,
+			      u32 len)
+{
+	*((*data)++) = _tag(UNIV, PRIM, OTS);
+	asn1_encode_length(data, len);
+	memcpy(*data, string, len);
+	*data += len;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_octet_string);
+
+/**
+ * asn1_encode_sequence - wrap a byte stream in an ASN.1 SEQUENCE
+ * @data: pointer to encode at
+ * @seq: data to be encoded as a sequence
+ * @len: length of the data to be encoded as a sequence
+ *
+ * Fill in a sequence.  To encode in place, pass NULL for @seq and -1
+ * for @len; then call again once the length is known (still with NULL
+ * for @seq). In order to avoid having to keep both before and after
+ * pointers, the repeat expects to be called with @data pointing to
+ * where the first encode placed it.
+ */
+void asn1_encode_sequence(unsigned char **data, const unsigned char *seq,
+			  int len)
+{
+	if (!seq && WARN(len > 127,
+			 "BUG: recode sequence is too big (>127)"))
+		return;
+	if (!seq && len > 0)
+		/* we're recoding, so move back to the start of the sequence */
+		*data -= 2;
+		
+	*((*data)++) = _tag(UNIV, CONS, SEQ);
+	asn1_encode_length(data, len);
+	if (!seq)
+		return;
+	memcpy(*data, seq, len);
+	*data += len;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_sequence);
+
+/**
+ * asn1_encode_boolean - encode a boolean value to ASN.1
+ * @data: pointer to encode at
+ * @val: the boolean true/false value
+ */
+void asn1_encode_boolean(unsigned char **data, bool val)
+{
+	*((*data)++) = _tag(UNIV, PRIM, BOOL);
+	asn1_encode_length(data, 1);
+	*((*data)++) = val ? 1 : 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_boolean);
-- 
2.16.4

[PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

We have a need in the TPM trusted keys to return the ASN.1 form of the
TPM key blob so it can be operated on by tools outside of the kernel.
To do that, we have to be able to read and write the key format.  The
current ASN.1 decoder does fine for reading, but we need pieces of an
ASN.1 encoder to return the key blob.

The current implementation only encodes the ASN.1 bits we actually need.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: updated API to use indefinite length, and made symbol exports gpl
---
 include/linux/asn1_encoder.h |  21 ++++
 lib/Makefile                 |   2 +-
 lib/asn1_encoder.c           | 258 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 280 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/asn1_encoder.h
 create mode 100644 lib/asn1_encoder.c

diff --git a/include/linux/asn1_encoder.h b/include/linux/asn1_encoder.h
new file mode 100644
index 000000000000..9cfb8035dc46
--- /dev/null
+++ b/include/linux/asn1_encoder.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _LINUX_ASN1_ENCODER_H
+#define _LINUX_ASN1_ENCODER_H
+
+#include <linux/types.h>
+#include <linux/asn1.h>
+#include <linux/asn1_ber_bytecode.h>
+
+#define asn1_oid_len(oid) (sizeof(oid)/sizeof(u32))
+void asn1_encode_integer(unsigned char **_data, s64 integer, int len);
+void asn1_encode_oid(unsigned char **_data, u32 oid[], int oid_len);
+void asn1_encode_tag(unsigned char **data, u32 tag,
+		     const unsigned char *string, int len);
+void asn1_encode_octet_string(unsigned char **data, const unsigned char *string,
+			      u32 len);
+void asn1_encode_sequence(unsigned char **data, const unsigned char *seq,
+			  int len);
+void asn1_encode_boolean(unsigned char **data, bool val);
+
+#endif
diff --git a/lib/Makefile b/lib/Makefile
index c2f0e2a4e4e8..515b35f92c3c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -233,7 +233,7 @@ obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o
 
 obj-$(CONFIG_PERCPU_TEST) += percpu_test.o
 
-obj-$(CONFIG_ASN1) += asn1_decoder.o
+obj-$(CONFIG_ASN1) += asn1_decoder.o asn1_encoder.o
 
 obj-$(CONFIG_FONT_SUPPORT) += fonts/
 
diff --git a/lib/asn1_encoder.c b/lib/asn1_encoder.c
new file mode 100644
index 000000000000..768cabf8bf76
--- /dev/null
+++ b/lib/asn1_encoder.c
@@ -0,0 +1,258 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Simple encoder primitives for ASN.1 BER/DER/CER
+ *
+ * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
+ */
+
+#include <linux/asn1_encoder.h>
+#include <linux/bug.h>
+#include <linux/string.h>
+#include <linux/module.h>
+
+/**
+ * asn1_encode_integer - encode positive integer to ASN.1
+ * @_data: pointer to the pointer to the data
+ * @integer: integer to be encoded
+ * @len: length of buffer
+ *
+ * This is a simplified encoder: it only currently does
+ * positive integers, but it should be simple enough to add the 
+ * negative case if a use comes along.
+ */
+void asn1_encode_integer(unsigned char **_data, s64 integer, int len)
+{
+	unsigned char *data = *_data, *d = &data[2];
+	int i;
+	bool found = false;
+
+	if (WARN(integer < 0,
+		 "BUG: asn1_encode_integer only supports positive integers"))
+		return;
+
+	if (WARN(len < 3,
+		 "BUG: buffer for integers must have at least 3 bytes"))
+		return;
+
+	len =- 2;
+
+	data[0] = _tag(UNIV, PRIM, INT);
+	if (integer == 0) {
+		*d++ = 0;
+		goto out;
+	}
+	for (i = sizeof(integer); i > 0 ; i--) {
+		int byte = integer >> (8*(i-1));
+
+		if (!found && byte == 0)
+			continue;
+		found = true;
+		if (byte & 0x80) {
+			/*
+			 * no check needed here, we already know we
+			 * have len >= 1
+			 */
+			*d++ = 0;
+			len--;
+		}
+		if (WARN(len == 0,
+			 "BUG buffer too short in asn1_encode_integer"))
+			return;
+		*d++ = byte;
+		len--;
+	}
+ out:
+	data[1] = d - data - 2;
+	*_data = d;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_integer);
+
+/* calculate the base 128 digit values setting the top bit of the first octet */
+static void asn1_encode_oid_digit(unsigned char **_data, u32 oid)
+{
+	int start = 7 + 7 + 7 + 7;
+	unsigned char *data = *_data;
+
+	/* quick case */
+	if (oid == 0) {
+		*data++ = 0x80;
+		goto out;
+	}
+
+	while (oid >> start == 0)
+		start -= 7;
+
+	while (start > 0) {
+		u8 byte;
+
+		byte = oid >> start;
+		oid = oid - (byte << start);
+		start -= 7;
+		byte |= 0x80;
+		*data++ = byte;
+	}
+	*data++ = oid;
+
+ out:
+	*_data = data;
+}
+
+/**
+ * asn1_encode_oid - encode an oid to ASN.1
+ * @_data: position to begin encoding at
+ * @oid: array of oids
+ * @oid_len: length of oid array
+ *
+ * this encodes an OID up to ASN.1 when presented as an array of OID values
+ */
+void asn1_encode_oid(unsigned char **_data, u32 oid[], int oid_len)
+{
+	unsigned char *data = *_data;
+	unsigned char *d = data + 2;
+	int i;
+
+	if (WARN(oid_len < 2, "OID must have at least two elements"))
+		return;
+	if (WARN(oid_len > 32, "OID is too large"))
+		return;
+
+	data[0] = _tag(UNIV, PRIM, OID);
+	*d++ = oid[0] * 40 + oid[1];
+	for (i = 2; i < oid_len; i++)
+		asn1_encode_oid_digit(&d, oid[i]);
+	data[1] = d - data - 2;
+	*_data = d;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_oid);
+
+static void asn1_encode_length(unsigned char **data, int len)
+{
+	if (len < 0) {
+		*((*data)++) = ASN1_INDEFINITE_LENGTH;
+		return;
+	}
+	if (len <= 0x7f) {
+		*((*data)++) = len;
+		return;
+	}
+	if (len <= 0xff) {
+		*((*data)++) = 0x81;
+		*((*data)++) = len & 0xff;
+		return;
+	}
+	if (len <= 0xffff) {
+		*((*data)++) = 0x82;
+		*((*data)++) = (len >> 8) & 0xff;
+		*((*data)++) = len & 0xff;
+		return;
+	}
+
+	if (WARN(len > 0xffffff, "ASN.1 length can't be > 0xffffff"))
+		return;
+
+	*((*data)++) = 0x83;
+	*((*data)++) = (len >> 16) & 0xff;
+	*((*data)++) = (len >> 8) & 0xff;
+	*((*data)++) = len & 0xff;
+}
+
+/**
+ * asn1_encode_tag - add a tag for optional or explicit value
+ * @data: pointer to place tag at
+ * @tag: tag to be placed
+ * @string: the data to be tagged
+ * @len: the length of the data to be tagged
+ *
+ * Note this currently only handles short form tags < 31.  To encode
+ * in place pass a NULL @string and -1 for @len; all this will do is
+ * add an indefinite length tag and update the data pointer to the
+ * place where the tag contents should be placed.  After the data is
+ * placed, repeat the prior statement but now with the known length.
+ * In order to avoid having to keep both before and after pointers,
+ * the repeat expects to be called with @data pointing to where the
+ * first encode placed it.
+ */
+void asn1_encode_tag(unsigned char **data, u32 tag,
+		     const unsigned char *string, int len)
+{
+	if (WARN(tag > 30, "ASN.1 tag can't be > 30"))
+		return;
+
+	if (!string && WARN(len > 127,
+			    "BUG: recode tag is too big (>127)"))
+		return;
+
+	if (!string && len > 0)
+		/* we're recoding, so move back to the start of the tag */
+		*data -= 2;
+
+	*((*data)++) = _tagn(CONT, CONS, tag);
+	asn1_encode_length(data, len);
+	if (!string)
+		return;
+	memcpy(*data, string, len);
+	*data += len;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_tag);
+
+/**
+ * asn1_encode_octet_string - encode an ASN.1 OCTET STRING
+ * @data: pointer to encode at
+ * @string: string to be encoded
+ * @len: length of string
+ *
+ * Note ASN.1 octet strings may contain zeros, so the length is obligatory.
+ */
+void asn1_encode_octet_string(unsigned char **data, const unsigned char *string,
+			      u32 len)
+{
+	*((*data)++) = _tag(UNIV, PRIM, OTS);
+	asn1_encode_length(data, len);
+	memcpy(*data, string, len);
+	*data += len;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_octet_string);
+
+/**
+ * asn1_encode_sequence - wrap a byte stream in an ASN.1 SEQUENCE
+ * @data: pointer to encode at
+ * @seq: data to be encoded as a sequence
+ * @len: length of the data to be encoded as a sequence
+ *
+ * Fill in a sequence.  To encode in place, pass NULL for @seq and -1
+ * for @len; then call again once the length is known (still with NULL
+ * for @seq). In order to avoid having to keep both before and after
+ * pointers, the repeat expects to be called with @data pointing to
+ * where the first encode placed it.
+ */
+void asn1_encode_sequence(unsigned char **data, const unsigned char *seq,
+			  int len)
+{
+	if (!seq && WARN(len > 127,
+			 "BUG: recode sequence is too big (>127)"))
+		return;
+	if (!seq && len > 0)
+		/* we're recoding, so move back to the start of the sequence */
+		*data -= 2;
+		
+	*((*data)++) = _tag(UNIV, CONS, SEQ);
+	asn1_encode_length(data, len);
+	if (!seq)
+		return;
+	memcpy(*data, seq, len);
+	*data += len;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_sequence);
+
+/**
+ * asn1_encode_boolean - encode a boolean value to ASN.1
+ * @data: pointer to encode at
+ * @val: the boolean true/false value
+ */
+void asn1_encode_boolean(unsigned char **data, bool val)
+{
+	*((*data)++) = _tag(UNIV, PRIM, BOOL);
+	asn1_encode_length(data, 1);
+	*((*data)++) = val ? 1 : 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_boolean);
-- 
2.16.4

[PATCH v2 3/8] oid_registry: Add TCG defined OIDS for TPM keys

[James Bottomley]

The TCG has defined an OID prefix "2.23.133.10.1" for the various TPM
key uses.  We've defined three of the available numbers:

2.23.133.10.1.3 TPM Loadable key.  This is an asymmetric key (Usually
		RSA2048 or Elliptic Curve) which can be imported by a
		TPM2_Load() operation.

2.23.133.10.1.4 TPM Importable Key.  This is an asymmetric key (Usually
		RSA2048 or Elliptic Curve) which can be imported by a
		TPM2_Import() operation.

Both loadable and importable keys are specific to a given TPM, the
difference is that a loadable key is wrapped with the symmetric
secret, so must have been created by the TPM itself.  An importable
key is wrapped with a DH shared secret, and may be created without
access to the TPM provided you know the public part of the parent key.

2.23.133.10.1.5 TPM Sealed Data.  This is a set of data (up to 128
		bytes) which is sealed by the TPM.  It usually
		represents a symmetric key and must be unsealed before
		use.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 include/linux/oid_registry.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/oid_registry.h b/include/linux/oid_registry.h
index 657d6bf2c064..a4cee888f9b0 100644
--- a/include/linux/oid_registry.h
+++ b/include/linux/oid_registry.h
@@ -107,6 +107,11 @@ enum OID {
 	OID_gostTC26Sign512B,		/* 1.2.643.7.1.2.1.2.2 */
 	OID_gostTC26Sign512C,		/* 1.2.643.7.1.2.1.2.3 */
 
+	/* TCG defined OIDS for TPM based keys */
+	OID_TPMLoadableKey,		/* 2.23.133.10.1.3 */
+	OID_TPMImporableKey,		/* 2.23.133.10.1.4 */
+	OID_TPMSealedData,		/* 2.23.133.10.1.5 */
+
 	OID__NR
 };
 
-- 
2.16.4

[PATCH v2 3/8] oid_registry: Add TCG defined OIDS for TPM keys

[James Bottomley]

The TCG has defined an OID prefix "2.23.133.10.1" for the various TPM
key uses.  We've defined three of the available numbers:

2.23.133.10.1.3 TPM Loadable key.  This is an asymmetric key (Usually
		RSA2048 or Elliptic Curve) which can be imported by a
		TPM2_Load() operation.

2.23.133.10.1.4 TPM Importable Key.  This is an asymmetric key (Usually
		RSA2048 or Elliptic Curve) which can be imported by a
		TPM2_Import() operation.

Both loadable and importable keys are specific to a given TPM, the
difference is that a loadable key is wrapped with the symmetric
secret, so must have been created by the TPM itself.  An importable
key is wrapped with a DH shared secret, and may be created without
access to the TPM provided you know the public part of the parent key.

2.23.133.10.1.5 TPM Sealed Data.  This is a set of data (up to 128
		bytes) which is sealed by the TPM.  It usually
		represents a symmetric key and must be unsealed before
		use.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 include/linux/oid_registry.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/oid_registry.h b/include/linux/oid_registry.h
index 657d6bf2c064..a4cee888f9b0 100644
--- a/include/linux/oid_registry.h
+++ b/include/linux/oid_registry.h
@@ -107,6 +107,11 @@ enum OID {
 	OID_gostTC26Sign512B,		/* 1.2.643.7.1.2.1.2.2 */
 	OID_gostTC26Sign512C,		/* 1.2.643.7.1.2.1.2.3 */
 
+	/* TCG defined OIDS for TPM based keys */
+	OID_TPMLoadableKey,		/* 2.23.133.10.1.3 */
+	OID_TPMImporableKey,		/* 2.23.133.10.1.4 */
+	OID_TPMSealedData,		/* 2.23.133.10.1.5 */
+
 	OID__NR
 };
 
-- 
2.16.4

[PATCH v2 4/8] security: keys: trusted: use ASN.1 tpm2 key format for the blobs

[James Bottomley]

Modify the tpm2 key format blob output to export and import in the
ASN.1 form for tpm2 sealed object keys.  For compatibility with prior
trusted keys, the importer will also accept two tpm2b quantities
representing the public and private parts of the key.  However, the
export via keyctl pipe will only output the ASN.1 format.

The benefit of the ASN.1 format is that it's a standard and thus the
exported key can be used by userspace tools.  The format includes
policy specifications, thus it gets us out of having to construct
policy handles in userspace and the format includes the parent meaning
you don't have to keep passing it in each time.

This patch only implements basic handling for the ASN.1 format, so
keys with passwords but no policy.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

v2: Updated encode API, added length checks
---
 security/keys/trusted-keys/Makefile       |   2 +-
 security/keys/trusted-keys/tpm2key.asn1   |  23 ++++
 security/keys/trusted-keys/trusted_tpm1.c |   2 +-
 security/keys/trusted-keys/trusted_tpm2.c | 181 +++++++++++++++++++++++++++++-
 4 files changed, 201 insertions(+), 7 deletions(-)
 create mode 100644 security/keys/trusted-keys/tpm2key.asn1

diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index 7b73cebbb378..e0198641eff2 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -5,4 +5,4 @@
 
 obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
 trusted-y += trusted_tpm1.o
-trusted-y += trusted_tpm2.o
+trusted-y += trusted_tpm2.o tpm2key.asn1.o
diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
new file mode 100644
index 000000000000..1851b7c80f08
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2key.asn1
@@ -0,0 +1,23 @@
+---
+--- Note: This isn't quite the definition in the standard
+---       However, the Linux asn.1 parser doesn't understand
+---       [2] EXPLICIT SEQUENCE OF OPTIONAL
+---       So there's an extra intermediate TPMPolicySequence
+---       definition to work around this
+
+TPMKey ::= SEQUENCE {
+	type		OBJECT IDENTIFIER ({tpmkey_type}),
+	emptyAuth	[0] EXPLICIT BOOLEAN OPTIONAL,
+	policy		[1] EXPLICIT TPMPolicySequence OPTIONAL,
+	secret		[2] EXPLICIT OCTET STRING OPTIONAL,
+	parent		INTEGER ({tpmkey_parent}),
+	pubkey		OCTET STRING ({tpmkey_pub}),
+	privkey		OCTET STRING ({tpmkey_priv})
+	}
+
+TPMPolicySequence ::= SEQUENCE OF TPMPolicy
+
+TPMPolicy ::= SEQUENCE {
+	commandCode		[0] EXPLICIT INTEGER,
+	commandPolicy		[1] EXPLICIT OCTET STRING
+	}
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index d2c5ec1e040b..d744a0d1cb89 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -991,7 +991,7 @@ static int trusted_instantiate(struct key *key,
 		goto out;
 	}
 
-	if (!options->keyhandle) {
+	if (!options->keyhandle && !tpm2) {
 		ret = -EINVAL;
 		goto out;
 	}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 08ec7f48f01d..6ae3197f767f 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -4,6 +4,8 @@
  * Copyright (C) 2014 Intel Corporation
  */
 
+#include <linux/asn1_encoder.h>
+#include <linux/oid_registry.h>
 #include <linux/string.h>
 #include <linux/err.h>
 #include <linux/tpm.h>
@@ -12,6 +14,10 @@
 #include <keys/trusted-type.h>
 #include <keys/trusted_tpm.h>
 
+#include <asm/unaligned.h>
+
+#include "tpm2key.asn1.h"
+
 static struct tpm2_hash tpm2_hash_map[] = {
 	{HASH_ALGO_SHA1, TPM_ALG_SHA1},
 	{HASH_ALGO_SHA256, TPM_ALG_SHA256},
@@ -20,6 +26,152 @@ static struct tpm2_hash tpm2_hash_map[] = {
 	{HASH_ALGO_SM3_256, TPM_ALG_SM3_256},
 };
 
+static u32 tpm2key_oid[] = { 2,23,133,10,1,5 };
+
+static int tpm2_key_encode(struct trusted_key_payload *payload,
+			   struct trusted_key_options *options,
+			   u8 *src, u32 len)
+{
+	const int SCRATCH_SIZE = PAGE_SIZE;
+	u8 *scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL);
+	u8 *work = scratch, *work1;
+	u8 *priv, *pub;
+	u16 priv_len, pub_len;
+
+	priv_len = get_unaligned_be16(src);
+	src += 2;
+	priv = src;
+	src += priv_len;
+	pub_len = get_unaligned_be16(src);
+	src += 2;
+	pub = src;
+
+	if (!scratch)
+		return -ENOMEM;
+
+	asn1_encode_oid(&work, tpm2key_oid, asn1_oid_len(tpm2key_oid));
+	if (options->blobauth[0] = 0) {
+		unsigned char bool[3], *w = bool;
+		/* tag 0 is emptyAuth */
+		asn1_encode_boolean(&w, true);
+		asn1_encode_tag(&work, 0, bool, w - bool);
+	}
+	asn1_encode_integer(&work, options->keyhandle,
+			    work - scratch + SCRATCH_SIZE);
+	/*
+	 * Assume both ovtet strings will encode to a 2 byte definite length
+	 *
+	 * Note: For a well behaved TPM, this warning should never
+	 * trigger, so if it does there's something nefarious going on
+	 */
+	if (WARN(work - scratch + pub_len + priv_len + 8 > SCRATCH_SIZE,
+		 "BUG: scratch buffer is too small"))
+		return -EINVAL;
+	asn1_encode_octet_string(&work, pub, pub_len);
+	asn1_encode_octet_string(&work, priv, priv_len);
+
+	work1 = payload->blob;
+	asn1_encode_sequence(&work1, scratch, work - scratch);
+
+	return work1 - payload->blob;
+}
+
+struct tpm2key_context {
+	u32 parent;
+	const u8 *pub;
+	u32 pub_len;
+	const u8 *priv;
+	u32 priv_len;
+};
+
+static int tpm2_key_decode(struct trusted_key_payload *payload,
+			   struct trusted_key_options *options,
+			   u8 **buf)
+{
+	int ret;
+	struct tpm2key_context ctx;
+	u8 *blob;
+
+	ret = asn1_ber_decoder(&tpm2key_decoder, &ctx, payload->blob,
+			       payload->blob_len);
+	if (ret < 0)
+		return ret;
+
+	if (ctx.priv_len + ctx.pub_len > MAX_BLOB_SIZE)
+		return -EINVAL;
+
+	blob = kmalloc(ctx.priv_len + ctx.pub_len + 4, GFP_KERNEL);
+	if (!blob)
+		return -ENOMEM;
+
+	*buf = blob;
+	options->keyhandle = ctx.parent;
+	put_unaligned_be16(ctx.priv_len, blob);
+	blob += 2;
+	memcpy(blob, ctx.priv, ctx.priv_len);
+	blob += ctx.priv_len;
+	put_unaligned_be16(ctx.pub_len, blob);
+	blob += 2;
+	memcpy(blob, ctx.pub, ctx.pub_len);
+
+	return 0;
+}
+
+int tpmkey_parent(void *context, size_t hdrlen,
+		  unsigned char tag,
+		  const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+	const u8 *v = value;
+	int i;
+
+	ctx->parent = 0;
+	for (i = 0; i < vlen; i++) {
+		ctx->parent <<= 8;
+		ctx->parent |= v[i];
+	}
+	return 0;
+}
+
+int tpmkey_type(void *context, size_t hdrlen,
+		unsigned char tag,
+		const void *value, size_t vlen)
+{
+	enum OID oid = look_up_OID(value, vlen);
+
+	if (oid != OID_TPMSealedData) {
+		char buffer[50];
+
+		sprint_oid(value, vlen, buffer, sizeof(buffer));
+		pr_debug("OID is \"%s\" which is not TPMSealedData\n",
+			 buffer);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+int tpmkey_pub(void *context, size_t hdrlen,
+	       unsigned char tag,
+	       const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+
+	ctx->pub = value;
+	ctx->pub_len = vlen;
+	return 0;
+}
+
+int tpmkey_priv(void *context, size_t hdrlen,
+		unsigned char tag,
+		const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+
+	ctx->priv = value;
+	ctx->priv_len = vlen;
+	return 0;
+}
+
 /**
  * tpm_buf_append_auth() - append TPMS_AUTH_COMMAND to the buffer.
  *
@@ -79,6 +231,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (i = ARRAY_SIZE(tpm2_hash_map))
 		return -EINVAL;
 
+	if (!options->keyhandle)
+		return -EINVAL;
+
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
 	if (rc)
 		return rc;
@@ -144,8 +299,10 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		goto out;
 	}
 
-	memcpy(payload->blob, &buf.data[TPM_HEADER_SIZE + 4], blob_len);
-	payload->blob_len = blob_len;
+	payload->blob_len +		tpm2_key_encode(payload, options,
+				&buf.data[TPM_HEADER_SIZE + 4],
+				blob_len);
 
 out:
 	tpm_buf_destroy(&buf);
@@ -156,6 +313,8 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		else
 			rc = -EPERM;
 	}
+	if (payload->blob_len < 0)
+		return payload->blob_len;
 
 	return rc;
 }
@@ -182,13 +341,23 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	unsigned int private_len;
 	unsigned int public_len;
 	unsigned int blob_len;
+	u8 *blob;
 	int rc;
 
-	private_len = be16_to_cpup((__be16 *) &payload->blob[0]);
+	rc = tpm2_key_decode(payload, options, &blob);
+	if (rc)
+		/* old form */
+		blob = payload->blob;
+
+	/* new format carries keyhandle but old format doesn't */
+	if (!options->keyhandle)
+		return -EINVAL;
+
+	private_len = be16_to_cpup((__be16 *) &blob[0]);
 	if (private_len > (payload->blob_len - 2))
 		return -E2BIG;
 
-	public_len = be16_to_cpup((__be16 *) &payload->blob[2 + private_len]);
+	public_len = be16_to_cpup((__be16 *) &blob[2 + private_len]);
 	blob_len = private_len + public_len + 4;
 	if (blob_len > payload->blob_len)
 		return -E2BIG;
@@ -204,7 +373,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 			     options->keyauth /* hmac */,
 			     TPM_DIGEST_SIZE);
 
-	tpm_buf_append(&buf, payload->blob, blob_len);
+	tpm_buf_append(&buf, blob, blob_len);
 
 	if (buf.flags & TPM_BUF_OVERFLOW) {
 		rc = -E2BIG;
@@ -217,6 +386,8 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
 
 out:
+	if (blob != payload->blob)
+		kfree(blob);
 	tpm_buf_destroy(&buf);
 
 	if (rc > 0)
-- 
2.16.4

[PATCH v2 4/8] security: keys: trusted: use ASN.1 tpm2 key format for the blobs

[James Bottomley]

Modify the tpm2 key format blob output to export and import in the
ASN.1 form for tpm2 sealed object keys.  For compatibility with prior
trusted keys, the importer will also accept two tpm2b quantities
representing the public and private parts of the key.  However, the
export via keyctl pipe will only output the ASN.1 format.

The benefit of the ASN.1 format is that it's a standard and thus the
exported key can be used by userspace tools.  The format includes
policy specifications, thus it gets us out of having to construct
policy handles in userspace and the format includes the parent meaning
you don't have to keep passing it in each time.

This patch only implements basic handling for the ASN.1 format, so
keys with passwords but no policy.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

v2: Updated encode API, added length checks
---
 security/keys/trusted-keys/Makefile       |   2 +-
 security/keys/trusted-keys/tpm2key.asn1   |  23 ++++
 security/keys/trusted-keys/trusted_tpm1.c |   2 +-
 security/keys/trusted-keys/trusted_tpm2.c | 181 +++++++++++++++++++++++++++++-
 4 files changed, 201 insertions(+), 7 deletions(-)
 create mode 100644 security/keys/trusted-keys/tpm2key.asn1

diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index 7b73cebbb378..e0198641eff2 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -5,4 +5,4 @@
 
 obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
 trusted-y += trusted_tpm1.o
-trusted-y += trusted_tpm2.o
+trusted-y += trusted_tpm2.o tpm2key.asn1.o
diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
new file mode 100644
index 000000000000..1851b7c80f08
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2key.asn1
@@ -0,0 +1,23 @@
+---
+--- Note: This isn't quite the definition in the standard
+---       However, the Linux asn.1 parser doesn't understand
+---       [2] EXPLICIT SEQUENCE OF OPTIONAL
+---       So there's an extra intermediate TPMPolicySequence
+---       definition to work around this
+
+TPMKey ::= SEQUENCE {
+	type		OBJECT IDENTIFIER ({tpmkey_type}),
+	emptyAuth	[0] EXPLICIT BOOLEAN OPTIONAL,
+	policy		[1] EXPLICIT TPMPolicySequence OPTIONAL,
+	secret		[2] EXPLICIT OCTET STRING OPTIONAL,
+	parent		INTEGER ({tpmkey_parent}),
+	pubkey		OCTET STRING ({tpmkey_pub}),
+	privkey		OCTET STRING ({tpmkey_priv})
+	}
+
+TPMPolicySequence ::= SEQUENCE OF TPMPolicy
+
+TPMPolicy ::= SEQUENCE {
+	commandCode		[0] EXPLICIT INTEGER,
+	commandPolicy		[1] EXPLICIT OCTET STRING
+	}
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index d2c5ec1e040b..d744a0d1cb89 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -991,7 +991,7 @@ static int trusted_instantiate(struct key *key,
 		goto out;
 	}
 
-	if (!options->keyhandle) {
+	if (!options->keyhandle && !tpm2) {
 		ret = -EINVAL;
 		goto out;
 	}
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 08ec7f48f01d..6ae3197f767f 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -4,6 +4,8 @@
  * Copyright (C) 2014 Intel Corporation
  */
 
+#include <linux/asn1_encoder.h>
+#include <linux/oid_registry.h>
 #include <linux/string.h>
 #include <linux/err.h>
 #include <linux/tpm.h>
@@ -12,6 +14,10 @@
 #include <keys/trusted-type.h>
 #include <keys/trusted_tpm.h>
 
+#include <asm/unaligned.h>
+
+#include "tpm2key.asn1.h"
+
 static struct tpm2_hash tpm2_hash_map[] = {
 	{HASH_ALGO_SHA1, TPM_ALG_SHA1},
 	{HASH_ALGO_SHA256, TPM_ALG_SHA256},
@@ -20,6 +26,152 @@ static struct tpm2_hash tpm2_hash_map[] = {
 	{HASH_ALGO_SM3_256, TPM_ALG_SM3_256},
 };
 
+static u32 tpm2key_oid[] = { 2,23,133,10,1,5 };
+
+static int tpm2_key_encode(struct trusted_key_payload *payload,
+			   struct trusted_key_options *options,
+			   u8 *src, u32 len)
+{
+	const int SCRATCH_SIZE = PAGE_SIZE;
+	u8 *scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL);
+	u8 *work = scratch, *work1;
+	u8 *priv, *pub;
+	u16 priv_len, pub_len;
+
+	priv_len = get_unaligned_be16(src);
+	src += 2;
+	priv = src;
+	src += priv_len;
+	pub_len = get_unaligned_be16(src);
+	src += 2;
+	pub = src;
+
+	if (!scratch)
+		return -ENOMEM;
+
+	asn1_encode_oid(&work, tpm2key_oid, asn1_oid_len(tpm2key_oid));
+	if (options->blobauth[0] == 0) {
+		unsigned char bool[3], *w = bool;
+		/* tag 0 is emptyAuth */
+		asn1_encode_boolean(&w, true);
+		asn1_encode_tag(&work, 0, bool, w - bool);
+	}
+	asn1_encode_integer(&work, options->keyhandle,
+			    work - scratch + SCRATCH_SIZE);
+	/*
+	 * Assume both ovtet strings will encode to a 2 byte definite length
+	 *
+	 * Note: For a well behaved TPM, this warning should never
+	 * trigger, so if it does there's something nefarious going on
+	 */
+	if (WARN(work - scratch + pub_len + priv_len + 8 > SCRATCH_SIZE,
+		 "BUG: scratch buffer is too small"))
+		return -EINVAL;
+	asn1_encode_octet_string(&work, pub, pub_len);
+	asn1_encode_octet_string(&work, priv, priv_len);
+
+	work1 = payload->blob;
+	asn1_encode_sequence(&work1, scratch, work - scratch);
+
+	return work1 - payload->blob;
+}
+
+struct tpm2key_context {
+	u32 parent;
+	const u8 *pub;
+	u32 pub_len;
+	const u8 *priv;
+	u32 priv_len;
+};
+
+static int tpm2_key_decode(struct trusted_key_payload *payload,
+			   struct trusted_key_options *options,
+			   u8 **buf)
+{
+	int ret;
+	struct tpm2key_context ctx;
+	u8 *blob;
+
+	ret = asn1_ber_decoder(&tpm2key_decoder, &ctx, payload->blob,
+			       payload->blob_len);
+	if (ret < 0)
+		return ret;
+
+	if (ctx.priv_len + ctx.pub_len > MAX_BLOB_SIZE)
+		return -EINVAL;
+
+	blob = kmalloc(ctx.priv_len + ctx.pub_len + 4, GFP_KERNEL);
+	if (!blob)
+		return -ENOMEM;
+
+	*buf = blob;
+	options->keyhandle = ctx.parent;
+	put_unaligned_be16(ctx.priv_len, blob);
+	blob += 2;
+	memcpy(blob, ctx.priv, ctx.priv_len);
+	blob += ctx.priv_len;
+	put_unaligned_be16(ctx.pub_len, blob);
+	blob += 2;
+	memcpy(blob, ctx.pub, ctx.pub_len);
+
+	return 0;
+}
+
+int tpmkey_parent(void *context, size_t hdrlen,
+		  unsigned char tag,
+		  const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+	const u8 *v = value;
+	int i;
+
+	ctx->parent = 0;
+	for (i = 0; i < vlen; i++) {
+		ctx->parent <<= 8;
+		ctx->parent |= v[i];
+	}
+	return 0;
+}
+
+int tpmkey_type(void *context, size_t hdrlen,
+		unsigned char tag,
+		const void *value, size_t vlen)
+{
+	enum OID oid = look_up_OID(value, vlen);
+
+	if (oid != OID_TPMSealedData) {
+		char buffer[50];
+
+		sprint_oid(value, vlen, buffer, sizeof(buffer));
+		pr_debug("OID is \"%s\" which is not TPMSealedData\n",
+			 buffer);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+int tpmkey_pub(void *context, size_t hdrlen,
+	       unsigned char tag,
+	       const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+
+	ctx->pub = value;
+	ctx->pub_len = vlen;
+	return 0;
+}
+
+int tpmkey_priv(void *context, size_t hdrlen,
+		unsigned char tag,
+		const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+
+	ctx->priv = value;
+	ctx->priv_len = vlen;
+	return 0;
+}
+
 /**
  * tpm_buf_append_auth() - append TPMS_AUTH_COMMAND to the buffer.
  *
@@ -79,6 +231,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (i == ARRAY_SIZE(tpm2_hash_map))
 		return -EINVAL;
 
+	if (!options->keyhandle)
+		return -EINVAL;
+
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
 	if (rc)
 		return rc;
@@ -144,8 +299,10 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		goto out;
 	}
 
-	memcpy(payload->blob, &buf.data[TPM_HEADER_SIZE + 4], blob_len);
-	payload->blob_len = blob_len;
+	payload->blob_len =
+		tpm2_key_encode(payload, options,
+				&buf.data[TPM_HEADER_SIZE + 4],
+				blob_len);
 
 out:
 	tpm_buf_destroy(&buf);
@@ -156,6 +313,8 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		else
 			rc = -EPERM;
 	}
+	if (payload->blob_len < 0)
+		return payload->blob_len;
 
 	return rc;
 }
@@ -182,13 +341,23 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	unsigned int private_len;
 	unsigned int public_len;
 	unsigned int blob_len;
+	u8 *blob;
 	int rc;
 
-	private_len = be16_to_cpup((__be16 *) &payload->blob[0]);
+	rc = tpm2_key_decode(payload, options, &blob);
+	if (rc)
+		/* old form */
+		blob = payload->blob;
+
+	/* new format carries keyhandle but old format doesn't */
+	if (!options->keyhandle)
+		return -EINVAL;
+
+	private_len = be16_to_cpup((__be16 *) &blob[0]);
 	if (private_len > (payload->blob_len - 2))
 		return -E2BIG;
 
-	public_len = be16_to_cpup((__be16 *) &payload->blob[2 + private_len]);
+	public_len = be16_to_cpup((__be16 *) &blob[2 + private_len]);
 	blob_len = private_len + public_len + 4;
 	if (blob_len > payload->blob_len)
 		return -E2BIG;
@@ -204,7 +373,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 			     options->keyauth /* hmac */,
 			     TPM_DIGEST_SIZE);
 
-	tpm_buf_append(&buf, payload->blob, blob_len);
+	tpm_buf_append(&buf, blob, blob_len);
 
 	if (buf.flags & TPM_BUF_OVERFLOW) {
 		rc = -E2BIG;
@@ -217,6 +386,8 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
 
 out:
+	if (blob != payload->blob)
+		kfree(blob);
 	tpm_buf_destroy(&buf);
 
 	if (rc > 0)
-- 
2.16.4

[PATCH v2 5/8] security: keys: trusted: Make sealed key properly interoperable

[James Bottomley]

The current implementation appends a migratable flag to the end of a
key, meaning the format isn't exactly interoperable because the using
party needs to know to strip this extra byte.  However, all other
consumers of TPM sealed blobs expect the unseal to return exactly the
key.  Since TPM2 keys have a key property flag that corresponds to
migratable, use that flag instead and make the actual key the only
sealed quantity.  This is secure because the key properties are bound
to a hash in the private part, so if they're altered the key won't
load.

Backwards compatibility is implemented by detecting whether we're
loading a new format key or not and correctly setting migratable from
the last byte of old format keys.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: added length checks to untrusted payload
---
 include/keys/trusted-type.h               |  1 +
 include/linux/tpm.h                       |  2 +
 security/keys/trusted-keys/trusted_tpm2.c | 69 ++++++++++++++++++++++---------
 3 files changed, 53 insertions(+), 19 deletions(-)

diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index a94c03a61d8f..4728e13aada8 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -22,6 +22,7 @@ struct trusted_key_payload {
 	unsigned int key_len;
 	unsigned int blob_len;
 	unsigned char migratable;
+	unsigned char old_format;
 	unsigned char key[MAX_KEY_SIZE + 1];
 	unsigned char blob[MAX_BLOB_SIZE];
 };
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 03e9b184411b..cd46ab27baa5 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -297,6 +297,8 @@ struct tpm_buf {
 };
 
 enum tpm2_object_attributes {
+	TPM2_OA_FIXED_TPM		= BIT(1),
+	TPM2_OA_FIXED_PARENT		= BIT(4),
 	TPM2_OA_USER_WITH_AUTH		= BIT(6),
 };
 
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 6ae3197f767f..6d2c5adbff18 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -218,6 +218,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	unsigned int blob_len;
 	struct tpm_buf buf;
 	u32 hash;
+	u32 flags;
 	int i;
 	int rc;
 
@@ -246,29 +247,30 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 			     TPM_DIGEST_SIZE);
 
 	/* sensitive */
-	tpm_buf_append_u16(&buf, 4 + TPM_DIGEST_SIZE + payload->key_len + 1);
+	tpm_buf_append_u16(&buf, 4 + TPM_DIGEST_SIZE + payload->key_len);
 
 	tpm_buf_append_u16(&buf, TPM_DIGEST_SIZE);
 	tpm_buf_append(&buf, options->blobauth, TPM_DIGEST_SIZE);
-	tpm_buf_append_u16(&buf, payload->key_len + 1);
+	tpm_buf_append_u16(&buf, payload->key_len);
 	tpm_buf_append(&buf, payload->key, payload->key_len);
-	tpm_buf_append_u8(&buf, payload->migratable);
 
 	/* public */
 	tpm_buf_append_u16(&buf, 14 + options->policydigest_len);
 	tpm_buf_append_u16(&buf, TPM_ALG_KEYEDHASH);
 	tpm_buf_append_u16(&buf, hash);
 
+	/* key properties */
+	flags = 0;
+	flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH;
+	flags |= payload->migratable ? (TPM2_OA_FIXED_TPM |
+					TPM2_OA_FIXED_PARENT) : 0;
+	tpm_buf_append_u32(&buf, flags);
+
 	/* policy */
-	if (options->policydigest_len) {
-		tpm_buf_append_u32(&buf, 0);
-		tpm_buf_append_u16(&buf, options->policydigest_len);
+	tpm_buf_append_u16(&buf, options->policydigest_len);
+	if (options->policydigest_len)
 		tpm_buf_append(&buf, options->policydigest,
 			       options->policydigest_len);
-	} else {
-		tpm_buf_append_u32(&buf, TPM2_OA_USER_WITH_AUTH);
-		tpm_buf_append_u16(&buf, 0);
-	}
 
 	/* public parameters */
 	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
@@ -341,23 +343,42 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	unsigned int private_len;
 	unsigned int public_len;
 	unsigned int blob_len;
-	u8 *blob;
+	u8 *blob, *pub;
 	int rc;
+	u32 attrs;
 
 	rc = tpm2_key_decode(payload, options, &blob);
-	if (rc)
+	if (rc) {
 		/* old form */
 		blob = payload->blob;
+		payload->old_format = 1;
+	}
 
 	/* new format carries keyhandle but old format doesn't */
 	if (!options->keyhandle)
 		return -EINVAL;
 
-	private_len = be16_to_cpup((__be16 *) &blob[0]);
-	if (private_len > (payload->blob_len - 2))
+	/* must be big enough for at least the two be16 size counts */
+	if (payload->blob_len < 4)
+		return -EINVAL;
+	private_len = get_unaligned_be16(blob);
+	/* must be big enough for following public_len */
+	if (private_len + 2 + 2 > (payload->blob_len))
+		return -E2BIG;
+
+	public_len = get_unaligned_be16(blob + 2 + private_len);
+	if (private_len + 2 + public_len + 2 > payload->blob_len)
 		return -E2BIG;
 
-	public_len = be16_to_cpup((__be16 *) &blob[2 + private_len]);
+	pub = blob + 2 + private_len + 2;
+	/* key attributes are always at offset 4 */
+	attrs = get_unaligned_be32(pub + 4);
+	if ((attrs & (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT)) =
+	    (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT))
+		payload->migratable = 0;
+	else
+		payload->migratable = 1;
+
 	blob_len = private_len + public_len + 4;
 	if (blob_len > payload->blob_len)
 		return -E2BIG;
@@ -438,7 +459,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	if (!rc) {
 		data_len = be16_to_cpup(
 			(__be16 *) &buf.data[TPM_HEADER_SIZE + 4]);
-		if (data_len < MIN_KEY_SIZE ||  data_len > MAX_KEY_SIZE + 1) {
+		if (data_len < MIN_KEY_SIZE ||  data_len > MAX_KEY_SIZE) {
 			rc = -EFAULT;
 			goto out;
 		}
@@ -449,9 +470,19 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 		}
 		data = &buf.data[TPM_HEADER_SIZE + 6];
 
-		memcpy(payload->key, data, data_len - 1);
-		payload->key_len = data_len - 1;
-		payload->migratable = data[data_len - 1];
+		if (payload->old_format) {
+			/* migratable flag is at the end of the key */
+			memcpy(payload->key, data, data_len - 1);
+			payload->key_len = data_len - 1;
+			payload->migratable = data[data_len - 1];
+		} else {
+			/*
+			 * migratable flag already collected from key
+			 * attributes
+			 */
+			memcpy(payload->key, data, data_len);
+			payload->key_len = data_len;
+		}
 	}
 
 out:
-- 
2.16.4

[PATCH v2 5/8] security: keys: trusted: Make sealed key properly interoperable

[James Bottomley]

The current implementation appends a migratable flag to the end of a
key, meaning the format isn't exactly interoperable because the using
party needs to know to strip this extra byte.  However, all other
consumers of TPM sealed blobs expect the unseal to return exactly the
key.  Since TPM2 keys have a key property flag that corresponds to
migratable, use that flag instead and make the actual key the only
sealed quantity.  This is secure because the key properties are bound
to a hash in the private part, so if they're altered the key won't
load.

Backwards compatibility is implemented by detecting whether we're
loading a new format key or not and correctly setting migratable from
the last byte of old format keys.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: added length checks to untrusted payload
---
 include/keys/trusted-type.h               |  1 +
 include/linux/tpm.h                       |  2 +
 security/keys/trusted-keys/trusted_tpm2.c | 69 ++++++++++++++++++++++---------
 3 files changed, 53 insertions(+), 19 deletions(-)

diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index a94c03a61d8f..4728e13aada8 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -22,6 +22,7 @@ struct trusted_key_payload {
 	unsigned int key_len;
 	unsigned int blob_len;
 	unsigned char migratable;
+	unsigned char old_format;
 	unsigned char key[MAX_KEY_SIZE + 1];
 	unsigned char blob[MAX_BLOB_SIZE];
 };
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 03e9b184411b..cd46ab27baa5 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -297,6 +297,8 @@ struct tpm_buf {
 };
 
 enum tpm2_object_attributes {
+	TPM2_OA_FIXED_TPM		= BIT(1),
+	TPM2_OA_FIXED_PARENT		= BIT(4),
 	TPM2_OA_USER_WITH_AUTH		= BIT(6),
 };
 
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 6ae3197f767f..6d2c5adbff18 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -218,6 +218,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	unsigned int blob_len;
 	struct tpm_buf buf;
 	u32 hash;
+	u32 flags;
 	int i;
 	int rc;
 
@@ -246,29 +247,30 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 			     TPM_DIGEST_SIZE);
 
 	/* sensitive */
-	tpm_buf_append_u16(&buf, 4 + TPM_DIGEST_SIZE + payload->key_len + 1);
+	tpm_buf_append_u16(&buf, 4 + TPM_DIGEST_SIZE + payload->key_len);
 
 	tpm_buf_append_u16(&buf, TPM_DIGEST_SIZE);
 	tpm_buf_append(&buf, options->blobauth, TPM_DIGEST_SIZE);
-	tpm_buf_append_u16(&buf, payload->key_len + 1);
+	tpm_buf_append_u16(&buf, payload->key_len);
 	tpm_buf_append(&buf, payload->key, payload->key_len);
-	tpm_buf_append_u8(&buf, payload->migratable);
 
 	/* public */
 	tpm_buf_append_u16(&buf, 14 + options->policydigest_len);
 	tpm_buf_append_u16(&buf, TPM_ALG_KEYEDHASH);
 	tpm_buf_append_u16(&buf, hash);
 
+	/* key properties */
+	flags = 0;
+	flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH;
+	flags |= payload->migratable ? (TPM2_OA_FIXED_TPM |
+					TPM2_OA_FIXED_PARENT) : 0;
+	tpm_buf_append_u32(&buf, flags);
+
 	/* policy */
-	if (options->policydigest_len) {
-		tpm_buf_append_u32(&buf, 0);
-		tpm_buf_append_u16(&buf, options->policydigest_len);
+	tpm_buf_append_u16(&buf, options->policydigest_len);
+	if (options->policydigest_len)
 		tpm_buf_append(&buf, options->policydigest,
 			       options->policydigest_len);
-	} else {
-		tpm_buf_append_u32(&buf, TPM2_OA_USER_WITH_AUTH);
-		tpm_buf_append_u16(&buf, 0);
-	}
 
 	/* public parameters */
 	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
@@ -341,23 +343,42 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	unsigned int private_len;
 	unsigned int public_len;
 	unsigned int blob_len;
-	u8 *blob;
+	u8 *blob, *pub;
 	int rc;
+	u32 attrs;
 
 	rc = tpm2_key_decode(payload, options, &blob);
-	if (rc)
+	if (rc) {
 		/* old form */
 		blob = payload->blob;
+		payload->old_format = 1;
+	}
 
 	/* new format carries keyhandle but old format doesn't */
 	if (!options->keyhandle)
 		return -EINVAL;
 
-	private_len = be16_to_cpup((__be16 *) &blob[0]);
-	if (private_len > (payload->blob_len - 2))
+	/* must be big enough for at least the two be16 size counts */
+	if (payload->blob_len < 4)
+		return -EINVAL;
+	private_len = get_unaligned_be16(blob);
+	/* must be big enough for following public_len */
+	if (private_len + 2 + 2 > (payload->blob_len))
+		return -E2BIG;
+
+	public_len = get_unaligned_be16(blob + 2 + private_len);
+	if (private_len + 2 + public_len + 2 > payload->blob_len)
 		return -E2BIG;
 
-	public_len = be16_to_cpup((__be16 *) &blob[2 + private_len]);
+	pub = blob + 2 + private_len + 2;
+	/* key attributes are always at offset 4 */
+	attrs = get_unaligned_be32(pub + 4);
+	if ((attrs & (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT)) ==
+	    (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT))
+		payload->migratable = 0;
+	else
+		payload->migratable = 1;
+
 	blob_len = private_len + public_len + 4;
 	if (blob_len > payload->blob_len)
 		return -E2BIG;
@@ -438,7 +459,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	if (!rc) {
 		data_len = be16_to_cpup(
 			(__be16 *) &buf.data[TPM_HEADER_SIZE + 4]);
-		if (data_len < MIN_KEY_SIZE ||  data_len > MAX_KEY_SIZE + 1) {
+		if (data_len < MIN_KEY_SIZE ||  data_len > MAX_KEY_SIZE) {
 			rc = -EFAULT;
 			goto out;
 		}
@@ -449,9 +470,19 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 		}
 		data = &buf.data[TPM_HEADER_SIZE + 6];
 
-		memcpy(payload->key, data, data_len - 1);
-		payload->key_len = data_len - 1;
-		payload->migratable = data[data_len - 1];
+		if (payload->old_format) {
+			/* migratable flag is at the end of the key */
+			memcpy(payload->key, data, data_len - 1);
+			payload->key_len = data_len - 1;
+			payload->migratable = data[data_len - 1];
+		} else {
+			/*
+			 * migratable flag already collected from key
+			 * attributes
+			 */
+			memcpy(payload->key, data, data_len);
+			payload->key_len = data_len;
+		}
 	}
 
 out:
-- 
2.16.4

[PATCH v2 6/8] security: keys: trusted: add PCR policy to TPM2 keys

[James Bottomley]

This commit adds the ability to specify a PCR lock policy to TPM2
keys.  There is a complexity in that the creator of the key must chose
either to use a PCR lock policy or to use authentication.  At the
current time they can't use both due to a complexity with the way
authentication works when policy registers are in use.  The way to
construct a pcrinfo statement for a key is simply to use the
TPMS_PCR_SELECT structure to specify the PCRs and follow this by a
hash of all their values in order of ascending PCR number.

For simplicity, we require the policy name hash and the hash used for
the PCRs to be the same.  Thus to construct a policy around the value
of the resettable PCR 16 using the sha1 bank, first reset the pcr to
zero giving a hash of all zeros as:

6768033e216468247bd031a0a2d9876d79818f8f

Then the TPMS_PCR_SELECT value for PCR 16 is

03000001

So create a new 32 byte key with a policy policy locking the key to
this value of PCR 16 with a parent key of 81000001 would be:

keyctl new 32 keyhandle=0x81000001 hash=sha1 pcrinfo\x030000016768033e216468247bd031a0a2d9876d79818f8f" @u

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: fix for new ASN.1 API eliminating hack in place and check lengths
---
 Documentation/security/keys/trusted-encrypted.rst |  25 +-
 include/keys/trusted-type.h                       |   5 +-
 include/linux/tpm.h                               |   5 +
 security/keys/Kconfig                             |   2 +
 security/keys/trusted-keys/Makefile               |   2 +-
 security/keys/trusted-keys/tpm2-policy.c          | 340 ++++++++++++++++++++++
 security/keys/trusted-keys/tpm2-policy.h          |  30 ++
 security/keys/trusted-keys/tpm2key.asn1           |   4 +-
 security/keys/trusted-keys/trusted_tpm1.c         |  32 +-
 security/keys/trusted-keys/trusted_tpm2.c         |  86 +++++-
 10 files changed, 480 insertions(+), 51 deletions(-)
 create mode 100644 security/keys/trusted-keys/tpm2-policy.c
 create mode 100644 security/keys/trusted-keys/tpm2-policy.h

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 50ac8bcd6970..1a3ca84ad3cd 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -60,19 +60,16 @@ Usage::
                      (40 ascii zeros)
        blobauth=     ascii hex auth for sealed data default 0x00...
                      (40 ascii zeros)
-       pcrinfo=	     ascii hex of PCR_INFO or PCR_INFO_LONG (no default)
+       pcrinfo=      ascii hex of PCR_INFO or PCR_INFO_LONG (no
+                     default) on TPM 1.2 and a TPMS_PCR_SELECTION
+                     coupled with a hash of all the selected PCRs on
+                     TPM 2.0 using the selected hash.
        pcrlock=	     pcr number to be extended to "lock" blob
        migratable=   0|1 indicating permission to reseal to new PCR values,
                      default 1 (resealing allowed)
        hash=         hash algorithm name as a string. For TPM 1.x the only
                      allowed value is sha1. For TPM 2.x the allowed values
                      are sha1, sha256, sha384, sha512 and sm3-256.
-       policydigest= digest for the authorization policy. must be calculated
-                     with the same hash algorithm as specified by the 'hash='
-                     option.
-       policyhandle= handle to an authorization policy session that defines the
-                     same policy and with the same hash algorithm as was used to
-                     seal the key.
 
 "keyctl print" returns an ascii hex copy of the sealed key, which is in standard
 TPM_STORED_DATA format.  The key length for new keys are always in bytes.
@@ -151,6 +148,20 @@ Load a trusted key from the saved blob::
     f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
     e4a8aea2b607ec96931e6f4d4fe563ba
 
+Create a trusted key on TPM 2.0 using an all zero value of PCR16 and
+using the NV storage root 81000001 as the parent::
+
+    $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo\x030000016768033e216468247bd031a0a2d9876d79818f8f" @u
+
+Note the TPMS_PCR_SELECT value for PCR 16 is 03000001 because all
+current TPMs have 24 PCRs, so the initial 03 says there are three
+following bytes of selection and then because the bytes are big
+endian, 16 is bit zero of byte 2. the hash is the sha1 sum of all
+zeros (the value of PCR 16)::
+
+    $ dd if=/dev/zero bs=1 count  2>/dev/null|sha1sum
+    6768033e216468247bd031a0a2d9876d79818f8f
+
 Reseal a trusted key under new pcr values::
 
     $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index 4728e13aada8..fc9c13802c06 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -14,9 +14,11 @@
 #define MIN_KEY_SIZE			32
 #define MAX_KEY_SIZE			128
 #define MAX_BLOB_SIZE			512
-#define MAX_PCRINFO_SIZE		64
+#define MAX_PCRINFO_SIZE		128
 #define MAX_DIGEST_SIZE			64
 
+#define TPM2_MAX_POLICIES		16
+
 struct trusted_key_payload {
 	struct rcu_head rcu;
 	unsigned int key_len;
@@ -25,6 +27,7 @@ struct trusted_key_payload {
 	unsigned char old_format;
 	unsigned char key[MAX_KEY_SIZE + 1];
 	unsigned char blob[MAX_BLOB_SIZE];
+	struct tpm2_policies *policies;
 };
 
 struct trusted_key_options {
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index cd46ab27baa5..e32e9728adce 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -222,10 +222,14 @@ enum tpm2_command_codes {
 	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
 	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
 	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
+	TPM2_CC_POLICY_AUTHVALUE	= 0x016B,
+	TPM2_CC_POLICY_COUNTER_TIMER	= 0x016D,
+	TPM2_CC_START_AUTH_SESS		= 0x0176,
 	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
 	TPM2_CC_GET_CAPABILITY	        = 0x017A,
 	TPM2_CC_GET_RANDOM	        = 0x017B,
 	TPM2_CC_PCR_READ	        = 0x017E,
+	TPM2_CC_POLICY_PCR		= 0x017F,
 	TPM2_CC_PCR_EXTEND	        = 0x0182,
 	TPM2_CC_EVENT_SEQUENCE_COMPLETE = 0x0185,
 	TPM2_CC_HASH_SEQUENCE_START     = 0x0186,
@@ -234,6 +238,7 @@ enum tpm2_command_codes {
 };
 
 enum tpm2_permanent_handles {
+	TPM2_RH_NULL		= 0x40000007,
 	TPM2_RS_PW		= 0x40000009,
 };
 
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index dd313438fecf..6c2f2c22b284 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -80,6 +80,8 @@ config TRUSTED_KEYS
 	select CRYPTO
 	select CRYPTO_HMAC
 	select CRYPTO_SHA1
+	select CRYPTO_SHA256
+	select CRYPTO_SHA512
 	select CRYPTO_HASH_INFO
 	help
 	  This option provides support for creating, sealing, and unsealing
diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index e0198641eff2..194febacf362 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -5,4 +5,4 @@
 
 obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
 trusted-y += trusted_tpm1.o
-trusted-y += trusted_tpm2.o tpm2key.asn1.o
+trusted-y += trusted_tpm2.o tpm2key.asn1.o tpm2-policy.o
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
new file mode 100644
index 000000000000..1c70f82ed170
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
+ */
+
+#include <linux/asn1_encoder.h>
+#include <linux/err.h>
+#include <linux/types.h>
+#include <linux/printk.h>
+#include <linux/string.h>
+#include <linux/tpm.h>
+
+#include <asm/unaligned.h>
+
+#include <crypto/hash.h>
+
+#include <keys/trusted-type.h>
+#include <keys/trusted_tpm.h>
+
+#include "tpm2key.asn1.h"
+#include "tpm2-policy.h"
+
+int tpmkey_code(void *context, size_t hdrlen,
+		unsigned char tag,
+		const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+	u32 code = 0;
+	const u8 *v = value;
+	int i;
+
+	for (i = 0; i < vlen; i++) {
+		code <<= 8;
+		code |= v[i];
+	}
+
+	ctx->policy_code[ctx->policy_count] = code;
+
+	return 0;
+}
+
+int tpmkey_policy(void *context, size_t hdrlen,
+		  unsigned char tag,
+		  const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+
+	ctx->policies[ctx->policy_count] = value;
+	ctx->policy_len[ctx->policy_count++] = vlen;
+
+	return 0;
+}
+
+/* we only support a limited number of policy statement so
+ * make sure we don't have anything we can't support
+ */
+static int tpm2_validate_policy(struct tpm2_policies *pols)
+{
+	int i;
+
+	if (pols->count = 0)
+		return 0;
+
+	for (i = 0; i < pols->count; i++) {
+		switch (pols->code[i]) {
+		case TPM2_CC_POLICY_COUNTER_TIMER:
+		case TPM2_CC_POLICY_PCR:
+		case TPM2_CC_POLICY_AUTHVALUE:
+			break;
+		default:
+			printk(KERN_INFO "tpm2 policy 0x%x is unsupported",
+			       pols->code[i]);
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
+/**
+ * tpmkey_process_policy - collect the policty from the context
+ * @ctx: the context to collect from
+ * @payload: the payload structure to place it in
+ *
+ * THis function sizes the policy statements and allocates space
+ * within the payload to receive them before copying them over.  It
+ * should be used after the ber decoder has completed successfully
+ */
+int tpmkey_policy_process(struct tpm2key_context *ctx,
+			  struct trusted_key_payload *payload)
+{
+	int tot_len = 0;
+	u8 *buf;
+	int i, ret, len = 0;
+	struct tpm2_policies *pols;
+
+	if (ctx->policy_count = 0)
+		return 0;
+
+	for (i = 0; i < ctx->policy_count; i++)
+		tot_len += ctx->policy_len[i];
+	tot_len += sizeof(*pols);
+
+	pols = kmalloc(tot_len, GFP_KERNEL);
+	if (!pols)
+		return -ENOMEM;
+
+	payload->policies = pols;
+	buf = (u8 *)(pols + 1);
+
+	for (i = 0; i < ctx->policy_count; i++) {
+		pols->policies[i] = &buf[len];
+		pols->len[i] = ctx->policy_len[i];
+		pols->code[i] = ctx->policy_code[i];
+		if (pols->len[i])
+			memcpy(pols->policies[i], ctx->policies[i],
+			       ctx->policy_len[i]);
+		len += ctx->policy_len[i];
+	}
+	pols->count = ctx->policy_count;
+
+	ret = tpm2_validate_policy(pols);
+	if (ret) {
+		kfree(pols);
+		payload->policies = NULL;
+	}
+
+	/* capture the hash and size */
+
+	/* the hash is the second algorithm */
+	pols->hash = get_unaligned_be16(&ctx->pub[2]);
+	/* and the digest appears after the attributes */
+	pols->hash_size = get_unaligned_be16(&ctx->pub[8]);
+
+	return ret;
+}
+
+int tpm2_generate_policy_digest(struct tpm2_policies *pols,
+				u32 hash, u8 *policydigest, u32 *plen)
+{
+	int i;
+	struct crypto_shash *tfm;
+	int rc;
+
+	if (pols->count = 0)
+		return 0;
+
+	tfm = crypto_alloc_shash(hash_algo_name[hash], 0, 0);
+	if (IS_ERR(tfm))
+		return PTR_ERR(tfm);
+
+	rc = crypto_shash_digestsize(tfm);
+	if (WARN(rc > MAX_DIGEST_SIZE,
+		 "BUG: trusted key code has alg %s with digest too large (%d)",
+		 hash_algo_name[hash], rc)) {
+		rc = -EINVAL;
+		goto err;
+	}
+	pols->hash = hash;
+	pols->hash_size = rc;
+	*plen = rc;
+
+	/* policy digests always start out all zeros */
+	memset(policydigest, 0, rc);
+
+	for (i = 0; i < pols->count; i++) {
+		u8 *policy = pols->policies[i];
+		int len = pols->len[i];
+		u32 cmd = pols->code[i];
+		u8 digest[MAX_DIGEST_SIZE];
+		u8 code[4];
+		SHASH_DESC_ON_STACK(sdesc, tfm);
+
+		sdesc->tfm = tfm;
+		rc = crypto_shash_init(sdesc);
+		if (rc)
+			goto err;
+
+		/* first hash the previous digest */
+		crypto_shash_update(sdesc, policydigest, *plen);
+		/* then hash the command code */
+		put_unaligned_be32(cmd, code);
+		crypto_shash_update(sdesc, code, 4);
+
+		/* commands that need special handling */
+		if (cmd = TPM2_CC_POLICY_COUNTER_TIMER) {
+			SHASH_DESC_ON_STACK(sdesc1, tfm);
+
+			sdesc1->tfm = tfm;
+
+			/* counter timer policies are double hashed */
+			crypto_shash_digest(sdesc1, policy, len,
+					    digest);
+			policy = digest;
+			len = *plen;
+		}
+		crypto_shash_update(sdesc, policy, len);
+		/* now output the intermediate to the policydigest */
+		crypto_shash_final(sdesc, policydigest);
+
+	}
+	rc = 0;
+
+ err:
+	crypto_free_shash(tfm);
+	return rc;
+}
+
+int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len)
+{
+	const int SCRATCH_SIZE = PAGE_SIZE;
+	u8 *buf = kmalloc(2 * SCRATCH_SIZE, GFP_KERNEL);
+	u8 *work = buf + SCRATCH_SIZE, *ptr;
+	int i;
+
+	if (!buf)
+		return -ENOMEM;
+
+	for (i = 0; i < pols->count; i++) {
+		u8 *seq, *tag;
+		u32 cmd = pols->code[i];
+
+		if (WARN(work - buf + 14 + pols->len[i] > 2 * SCRATCH_SIZE,
+			 "BUG: scratch buffer is too small"))
+			return -EINVAL;
+
+		asn1_encode_sequence(&work, NULL, -1);
+		seq = work;
+
+		asn1_encode_tag(&work, 0, NULL, -1);
+		tag = work;
+		asn1_encode_integer(&work, cmd,
+				    work - buf + SCRATCH_SIZE);
+		asn1_encode_tag(&tag, 0, NULL, work - tag);
+
+		asn1_encode_tag(&work, 1, NULL, -1);
+		tag = work;
+		asn1_encode_octet_string(&work, pols->policies[i],
+					 pols->len[i]);
+		asn1_encode_tag(&tag, 1, NULL, work - tag);
+
+		asn1_encode_sequence(&seq, NULL, work - seq);
+	}
+	ptr = buf;
+	asn1_encode_sequence(&ptr, buf + PAGE_SIZE, work - buf - PAGE_SIZE);
+	*data = buf;
+	*len = ptr - buf;
+
+	return 0;
+}
+
+int tpm2_start_policy_session(struct tpm_chip *chip, u16 hash, u32 *handle)
+{
+	struct tpm_buf buf;
+	int rc;
+	int i;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
+	if (rc)
+		return rc;
+
+	/* NULL salt key handle */
+	tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+	/* NULL bind key handle */
+	tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+	/* empty nonce caller */
+	tpm_buf_append_u16(&buf, 20);
+	for (i = 0; i < 20; i++)
+		tpm_buf_append_u8(&buf, 0);
+	/* empty auth */
+	tpm_buf_append_u16(&buf, 0);
+	/* session type policy */
+	tpm_buf_append_u8(&buf, 0x01);
+
+	/* symmetric encryption parameters */
+	/* symmetric algorithm  */
+	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
+	/* hash algorithm for session */
+	tpm_buf_append_u16(&buf, hash);
+
+	rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+	if (rc)
+		goto out;
+
+	*handle = get_unaligned_be32(buf.data + TPM_HEADER_SIZE);
+ out:
+	tpm_buf_destroy(&buf);
+
+	return rc <= 0 ? rc : -EPERM;
+}
+
+int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
+			    u32 *handle)
+{
+	int i, rc;
+	const char *failure;
+
+	rc = tpm2_start_policy_session(chip, pols->hash, handle);
+	if (rc)
+		return rc;
+
+	for (i = 0; i < pols->count; i++) {
+		u32 cmd = pols->code[i];
+		struct tpm_buf buf;
+
+		rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, cmd);
+		if (rc)
+			return rc;
+
+		tpm_buf_append_u32(&buf, *handle);
+
+		switch (cmd) {
+		case TPM2_CC_POLICY_PCR:
+			failure = "PCR";
+			/*
+			 * for reasons best known to the TCG we have
+			 * to reverse the two arguments to send to the
+			 * policy command
+			 */
+			tpm_buf_append_u16(&buf, pols->hash_size);
+			tpm_buf_append(&buf, pols->policies[i] + pols->len[i] -
+				       pols->hash_size, pols->hash_size);
+			tpm_buf_append(&buf, pols->policies[i],
+				       pols->len[i] - pols->hash_size);
+			break;
+		default:
+			failure = "unknown policy";
+			break;
+		}
+		rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+		tpm_buf_destroy(&buf);
+		if (rc) {
+			printk(KERN_NOTICE "TPM policy %s failed, rc=%d\n",
+			       failure, rc);
+			tpm2_flush_context(chip, *handle);
+			*handle = 0;
+			return -EPERM;
+		}
+	}
+	return 0;
+}
diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
new file mode 100644
index 000000000000..152c948743f3
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2-policy.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+struct tpm2key_context {
+	u32 parent;
+	const u8 *pub;
+	u32 pub_len;
+	const u8 *priv;
+	u32 priv_len;
+	const u8 *policies[TPM2_MAX_POLICIES];
+	u32 policy_code[TPM2_MAX_POLICIES];
+	u16 policy_len[TPM2_MAX_POLICIES];
+	u8 policy_count;
+};
+
+struct tpm2_policies {
+	u32 code[TPM2_MAX_POLICIES];
+	u8 *policies[TPM2_MAX_POLICIES];
+	u16 len[TPM2_MAX_POLICIES];
+	u8 count;
+	u16 hash;
+	u16 hash_size;
+};
+
+int tpmkey_policy_process(struct tpm2key_context *ctx,
+			  struct trusted_key_payload *payload);
+int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
+				u8 *policydigest, u32 *plen);
+int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
+int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
+			    u32 *handle);
diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
index 1851b7c80f08..f930fd812db3 100644
--- a/security/keys/trusted-keys/tpm2key.asn1
+++ b/security/keys/trusted-keys/tpm2key.asn1
@@ -18,6 +18,6 @@ TPMKey ::= SEQUENCE {
 TPMPolicySequence ::= SEQUENCE OF TPMPolicy
 
 TPMPolicy ::= SEQUENCE {
-	commandCode		[0] EXPLICIT INTEGER,
-	commandPolicy		[1] EXPLICIT OCTET STRING
+	commandCode		[0] EXPLICIT INTEGER ({tpmkey_code}),
+	commandPolicy		[1] EXPLICIT OCTET STRING ({tpmkey_policy})
 	}
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index d744a0d1cb89..6290e611b632 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -707,8 +707,6 @@ enum {
 	Opt_keyhandle, Opt_keyauth, Opt_blobauth,
 	Opt_pcrinfo, Opt_pcrlock, Opt_migratable,
 	Opt_hash,
-	Opt_policydigest,
-	Opt_policyhandle,
 };
 
 static const match_table_t key_tokens = {
@@ -722,8 +720,6 @@ static const match_table_t key_tokens = {
 	{Opt_pcrlock, "pcrlock=%s"},
 	{Opt_migratable, "migratable=%s"},
 	{Opt_hash, "hash=%s"},
-	{Opt_policydigest, "policydigest=%s"},
-	{Opt_policyhandle, "policyhandle=%s"},
 	{Opt_err, NULL}
 };
 
@@ -738,7 +734,6 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 	unsigned long handle;
 	unsigned long lock;
 	unsigned long token_mask = 0;
-	unsigned int digest_len;
 	int i;
 	int tpm2;
 
@@ -801,8 +796,6 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 			opt->pcrlock = lock;
 			break;
 		case Opt_hash:
-			if (test_bit(Opt_policydigest, &token_mask))
-				return -EINVAL;
 			for (i = 0; i < HASH_ALGO__LAST; i++) {
 				if (!strcmp(args[0].from, hash_algo_name[i])) {
 					opt->hash = i;
@@ -816,24 +809,6 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 				return -EINVAL;
 			}
 			break;
-		case Opt_policydigest:
-			digest_len = hash_digest_size[opt->hash];
-			if (!tpm2 || strlen(args[0].from) != (2 * digest_len))
-				return -EINVAL;
-			res = hex2bin(opt->policydigest, args[0].from,
-				      digest_len);
-			if (res < 0)
-				return -EINVAL;
-			opt->policydigest_len = digest_len;
-			break;
-		case Opt_policyhandle:
-			if (!tpm2)
-				return -EINVAL;
-			res = kstrtoul(args[0].from, 16, &handle);
-			if (res < 0)
-				return -EINVAL;
-			opt->policyhandle = handle;
-			break;
 		default:
 			return -EINVAL;
 		}
@@ -1045,6 +1020,7 @@ static void trusted_rcu_free(struct rcu_head *rcu)
 	struct trusted_key_payload *p;
 
 	p = container_of(rcu, struct trusted_key_payload, rcu);
+	kzfree(p->policies);
 	kzfree(p);
 }
 
@@ -1164,7 +1140,11 @@ static long trusted_read(const struct key *key, char __user *buffer,
  */
 static void trusted_destroy(struct key *key)
 {
-	kzfree(key->payload.data[0]);
+	struct trusted_key_payload *p;
+
+	p = key->payload.data[0];
+	kzfree(p->policies);
+	kzfree(p);
 }
 
 struct key_type key_type_trusted = {
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 6d2c5adbff18..ffdd5bf27ea7 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -17,6 +17,7 @@
 #include <asm/unaligned.h>
 
 #include "tpm2key.asn1.h"
+#include "tpm2-policy.h"
 
 static struct tpm2_hash tpm2_hash_map[] = {
 	{HASH_ALGO_SHA1, TPM_ALG_SHA1},
@@ -56,17 +57,34 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 		asn1_encode_boolean(&w, true);
 		asn1_encode_tag(&work, 0, bool, w - bool);
 	}
-	asn1_encode_integer(&work, options->keyhandle,
-			    work - scratch + SCRATCH_SIZE);
+	if (payload->policies) {
+		u8 *encoded_pols;
+		u32 encoded_pol_len;
+		int ret;
+
+		ret = tpm2_encode_policy(payload->policies, &encoded_pols,
+					 &encoded_pol_len);
+
+		if (ret) {
+			return ret;
+		} else {
+			asn1_encode_tag(&work, 1, encoded_pols,
+					encoded_pol_len);
+			kfree(encoded_pols);
+		}
+	}
 	/*
 	 * Assume both ovtet strings will encode to a 2 byte definite length
 	 *
 	 * Note: For a well behaved TPM, this warning should never
 	 * trigger, so if it does there's something nefarious going on
 	 */
-	if (WARN(work - scratch + pub_len + priv_len + 8 > SCRATCH_SIZE,
+	if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE,
 		 "BUG: scratch buffer is too small"))
 		return -EINVAL;
+
+	asn1_encode_integer(&work, options->keyhandle,
+			    SCRATCH_SIZE - (work - scratch));
 	asn1_encode_octet_string(&work, pub, pub_len);
 	asn1_encode_octet_string(&work, priv, priv_len);
 
@@ -76,14 +94,6 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 	return work1 - payload->blob;
 }
 
-struct tpm2key_context {
-	u32 parent;
-	const u8 *pub;
-	u32 pub_len;
-	const u8 *priv;
-	u32 priv_len;
-};
-
 static int tpm2_key_decode(struct trusted_key_payload *payload,
 			   struct trusted_key_options *options,
 			   u8 **buf)
@@ -92,6 +102,8 @@ static int tpm2_key_decode(struct trusted_key_payload *payload,
 	struct tpm2key_context ctx;
 	u8 *blob;
 
+	memset(&ctx, 0, sizeof(ctx));
+
 	ret = asn1_ber_decoder(&tpm2key_decoder, &ctx, payload->blob,
 			       payload->blob_len);
 	if (ret < 0)
@@ -104,6 +116,12 @@ static int tpm2_key_decode(struct trusted_key_payload *payload,
 	if (!blob)
 		return -ENOMEM;
 
+	ret = tpmkey_policy_process(&ctx, payload);
+	if (ret) {
+		kfree(blob);
+		return ret;
+	}
+
 	*buf = blob;
 	options->keyhandle = ctx.parent;
 	put_unaligned_be16(ctx.priv_len, blob);
@@ -235,6 +253,37 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (!options->keyhandle)
 		return -EINVAL;
 
+	if (options->pcrinfo_len != 0) {
+		struct tpm2_policies *pols;
+		static u8 *scratch;
+		/* 4 array len, 2 hash alg */
+		const int len = 4 + 2 + options->pcrinfo_len;
+
+		pols = kmalloc(sizeof(*pols) + len, GFP_KERNEL);
+		if (!pols)
+			return -ENOMEM;
+
+		pols->count = 1;
+		pols->len[0] = len;
+		scratch = (u8 *)(pols + 1);
+		pols->policies[0] = scratch;
+		pols->code[0] = TPM2_CC_POLICY_PCR;
+
+		put_unaligned_be32(1, &scratch[0]);
+		put_unaligned_be16(hash, &scratch[4]);
+		memcpy(&scratch[6], options->pcrinfo, options->pcrinfo_len);
+		payload->policies = pols;
+	}
+
+	if (payload->policies) {
+		rc = tpm2_generate_policy_digest(payload->policies,
+						 options->hash,
+						 options->policydigest,
+						 &options->policydigest_len);
+		if (rc)
+			return rc;
+	}
+
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
 	if (rc)
 		return rc;
@@ -438,21 +487,30 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	u16 data_len;
 	u8 *data;
 	int rc;
+	u32 policyhandle = 0;
 
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
 	if (rc)
 		return rc;
 
+	if (payload->policies) {
+		rc = tpm2_get_policy_session(chip, payload->policies,
+					     &policyhandle);
+		if (rc)
+			return rc;
+	}
+
 	tpm_buf_append_u32(&buf, blob_handle);
 	tpm2_buf_append_auth(&buf,
-			     options->policyhandle ?
-			     options->policyhandle : TPM2_RS_PW,
+			     policyhandle ?
+			     policyhandle : TPM2_RS_PW,
 			     NULL /* nonce */, 0,
 			     TPM2_SA_CONTINUE_SESSION,
 			     options->blobauth /* hmac */,
-			     TPM_DIGEST_SIZE);
+			     policyhandle ? 0 : TPM_DIGEST_SIZE);
 
 	rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+	tpm2_flush_context(chip, policyhandle);
 	if (rc > 0)
 		rc = -EPERM;
 
-- 
2.16.4

[PATCH v2 6/8] security: keys: trusted: add PCR policy to TPM2 keys

[James Bottomley]

This commit adds the ability to specify a PCR lock policy to TPM2
keys.  There is a complexity in that the creator of the key must chose
either to use a PCR lock policy or to use authentication.  At the
current time they can't use both due to a complexity with the way
authentication works when policy registers are in use.  The way to
construct a pcrinfo statement for a key is simply to use the
TPMS_PCR_SELECT structure to specify the PCRs and follow this by a
hash of all their values in order of ascending PCR number.

For simplicity, we require the policy name hash and the hash used for
the PCRs to be the same.  Thus to construct a policy around the value
of the resettable PCR 16 using the sha1 bank, first reset the pcr to
zero giving a hash of all zeros as:

6768033e216468247bd031a0a2d9876d79818f8f

Then the TPMS_PCR_SELECT value for PCR 16 is

03000001

So create a new 32 byte key with a policy policy locking the key to
this value of PCR 16 with a parent key of 81000001 would be:

keyctl new 32 keyhandle=0x81000001 hash=sha1 pcrinfo=030000016768033e216468247bd031a0a2d9876d79818f8f" @u

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: fix for new ASN.1 API eliminating hack in place and check lengths
---
 Documentation/security/keys/trusted-encrypted.rst |  25 +-
 include/keys/trusted-type.h                       |   5 +-
 include/linux/tpm.h                               |   5 +
 security/keys/Kconfig                             |   2 +
 security/keys/trusted-keys/Makefile               |   2 +-
 security/keys/trusted-keys/tpm2-policy.c          | 340 ++++++++++++++++++++++
 security/keys/trusted-keys/tpm2-policy.h          |  30 ++
 security/keys/trusted-keys/tpm2key.asn1           |   4 +-
 security/keys/trusted-keys/trusted_tpm1.c         |  32 +-
 security/keys/trusted-keys/trusted_tpm2.c         |  86 +++++-
 10 files changed, 480 insertions(+), 51 deletions(-)
 create mode 100644 security/keys/trusted-keys/tpm2-policy.c
 create mode 100644 security/keys/trusted-keys/tpm2-policy.h

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 50ac8bcd6970..1a3ca84ad3cd 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -60,19 +60,16 @@ Usage::
                      (40 ascii zeros)
        blobauth=     ascii hex auth for sealed data default 0x00...
                      (40 ascii zeros)
-       pcrinfo=	     ascii hex of PCR_INFO or PCR_INFO_LONG (no default)
+       pcrinfo=      ascii hex of PCR_INFO or PCR_INFO_LONG (no
+                     default) on TPM 1.2 and a TPMS_PCR_SELECTION
+                     coupled with a hash of all the selected PCRs on
+                     TPM 2.0 using the selected hash.
        pcrlock=	     pcr number to be extended to "lock" blob
        migratable=   0|1 indicating permission to reseal to new PCR values,
                      default 1 (resealing allowed)
        hash=         hash algorithm name as a string. For TPM 1.x the only
                      allowed value is sha1. For TPM 2.x the allowed values
                      are sha1, sha256, sha384, sha512 and sm3-256.
-       policydigest= digest for the authorization policy. must be calculated
-                     with the same hash algorithm as specified by the 'hash='
-                     option.
-       policyhandle= handle to an authorization policy session that defines the
-                     same policy and with the same hash algorithm as was used to
-                     seal the key.
 
 "keyctl print" returns an ascii hex copy of the sealed key, which is in standard
 TPM_STORED_DATA format.  The key length for new keys are always in bytes.
@@ -151,6 +148,20 @@ Load a trusted key from the saved blob::
     f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
     e4a8aea2b607ec96931e6f4d4fe563ba
 
+Create a trusted key on TPM 2.0 using an all zero value of PCR16 and
+using the NV storage root 81000001 as the parent::
+
+    $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 pcrinfo=030000016768033e216468247bd031a0a2d9876d79818f8f" @u
+
+Note the TPMS_PCR_SELECT value for PCR 16 is 03000001 because all
+current TPMs have 24 PCRs, so the initial 03 says there are three
+following bytes of selection and then because the bytes are big
+endian, 16 is bit zero of byte 2. the hash is the sha1 sum of all
+zeros (the value of PCR 16)::
+
+    $ dd if=/dev/zero bs=1 count=20 2>/dev/null|sha1sum
+    6768033e216468247bd031a0a2d9876d79818f8f
+
 Reseal a trusted key under new pcr values::
 
     $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index 4728e13aada8..fc9c13802c06 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -14,9 +14,11 @@
 #define MIN_KEY_SIZE			32
 #define MAX_KEY_SIZE			128
 #define MAX_BLOB_SIZE			512
-#define MAX_PCRINFO_SIZE		64
+#define MAX_PCRINFO_SIZE		128
 #define MAX_DIGEST_SIZE			64
 
+#define TPM2_MAX_POLICIES		16
+
 struct trusted_key_payload {
 	struct rcu_head rcu;
 	unsigned int key_len;
@@ -25,6 +27,7 @@ struct trusted_key_payload {
 	unsigned char old_format;
 	unsigned char key[MAX_KEY_SIZE + 1];
 	unsigned char blob[MAX_BLOB_SIZE];
+	struct tpm2_policies *policies;
 };
 
 struct trusted_key_options {
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index cd46ab27baa5..e32e9728adce 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -222,10 +222,14 @@ enum tpm2_command_codes {
 	TPM2_CC_CONTEXT_LOAD	        = 0x0161,
 	TPM2_CC_CONTEXT_SAVE	        = 0x0162,
 	TPM2_CC_FLUSH_CONTEXT	        = 0x0165,
+	TPM2_CC_POLICY_AUTHVALUE	= 0x016B,
+	TPM2_CC_POLICY_COUNTER_TIMER	= 0x016D,
+	TPM2_CC_START_AUTH_SESS		= 0x0176,
 	TPM2_CC_VERIFY_SIGNATURE        = 0x0177,
 	TPM2_CC_GET_CAPABILITY	        = 0x017A,
 	TPM2_CC_GET_RANDOM	        = 0x017B,
 	TPM2_CC_PCR_READ	        = 0x017E,
+	TPM2_CC_POLICY_PCR		= 0x017F,
 	TPM2_CC_PCR_EXTEND	        = 0x0182,
 	TPM2_CC_EVENT_SEQUENCE_COMPLETE = 0x0185,
 	TPM2_CC_HASH_SEQUENCE_START     = 0x0186,
@@ -234,6 +238,7 @@ enum tpm2_command_codes {
 };
 
 enum tpm2_permanent_handles {
+	TPM2_RH_NULL		= 0x40000007,
 	TPM2_RS_PW		= 0x40000009,
 };
 
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index dd313438fecf..6c2f2c22b284 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -80,6 +80,8 @@ config TRUSTED_KEYS
 	select CRYPTO
 	select CRYPTO_HMAC
 	select CRYPTO_SHA1
+	select CRYPTO_SHA256
+	select CRYPTO_SHA512
 	select CRYPTO_HASH_INFO
 	help
 	  This option provides support for creating, sealing, and unsealing
diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index e0198641eff2..194febacf362 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -5,4 +5,4 @@
 
 obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
 trusted-y += trusted_tpm1.o
-trusted-y += trusted_tpm2.o tpm2key.asn1.o
+trusted-y += trusted_tpm2.o tpm2key.asn1.o tpm2-policy.o
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
new file mode 100644
index 000000000000..1c70f82ed170
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
+ */
+
+#include <linux/asn1_encoder.h>
+#include <linux/err.h>
+#include <linux/types.h>
+#include <linux/printk.h>
+#include <linux/string.h>
+#include <linux/tpm.h>
+
+#include <asm/unaligned.h>
+
+#include <crypto/hash.h>
+
+#include <keys/trusted-type.h>
+#include <keys/trusted_tpm.h>
+
+#include "tpm2key.asn1.h"
+#include "tpm2-policy.h"
+
+int tpmkey_code(void *context, size_t hdrlen,
+		unsigned char tag,
+		const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+	u32 code = 0;
+	const u8 *v = value;
+	int i;
+
+	for (i = 0; i < vlen; i++) {
+		code <<= 8;
+		code |= v[i];
+	}
+
+	ctx->policy_code[ctx->policy_count] = code;
+
+	return 0;
+}
+
+int tpmkey_policy(void *context, size_t hdrlen,
+		  unsigned char tag,
+		  const void *value, size_t vlen)
+{
+	struct tpm2key_context *ctx = context;
+
+	ctx->policies[ctx->policy_count] = value;
+	ctx->policy_len[ctx->policy_count++] = vlen;
+
+	return 0;
+}
+
+/* we only support a limited number of policy statement so
+ * make sure we don't have anything we can't support
+ */
+static int tpm2_validate_policy(struct tpm2_policies *pols)
+{
+	int i;
+
+	if (pols->count == 0)
+		return 0;
+
+	for (i = 0; i < pols->count; i++) {
+		switch (pols->code[i]) {
+		case TPM2_CC_POLICY_COUNTER_TIMER:
+		case TPM2_CC_POLICY_PCR:
+		case TPM2_CC_POLICY_AUTHVALUE:
+			break;
+		default:
+			printk(KERN_INFO "tpm2 policy 0x%x is unsupported",
+			       pols->code[i]);
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
+/**
+ * tpmkey_process_policy - collect the policty from the context
+ * @ctx: the context to collect from
+ * @payload: the payload structure to place it in
+ *
+ * THis function sizes the policy statements and allocates space
+ * within the payload to receive them before copying them over.  It
+ * should be used after the ber decoder has completed successfully
+ */
+int tpmkey_policy_process(struct tpm2key_context *ctx,
+			  struct trusted_key_payload *payload)
+{
+	int tot_len = 0;
+	u8 *buf;
+	int i, ret, len = 0;
+	struct tpm2_policies *pols;
+
+	if (ctx->policy_count == 0)
+		return 0;
+
+	for (i = 0; i < ctx->policy_count; i++)
+		tot_len += ctx->policy_len[i];
+	tot_len += sizeof(*pols);
+
+	pols = kmalloc(tot_len, GFP_KERNEL);
+	if (!pols)
+		return -ENOMEM;
+
+	payload->policies = pols;
+	buf = (u8 *)(pols + 1);
+
+	for (i = 0; i < ctx->policy_count; i++) {
+		pols->policies[i] = &buf[len];
+		pols->len[i] = ctx->policy_len[i];
+		pols->code[i] = ctx->policy_code[i];
+		if (pols->len[i])
+			memcpy(pols->policies[i], ctx->policies[i],
+			       ctx->policy_len[i]);
+		len += ctx->policy_len[i];
+	}
+	pols->count = ctx->policy_count;
+
+	ret = tpm2_validate_policy(pols);
+	if (ret) {
+		kfree(pols);
+		payload->policies = NULL;
+	}
+
+	/* capture the hash and size */
+
+	/* the hash is the second algorithm */
+	pols->hash = get_unaligned_be16(&ctx->pub[2]);
+	/* and the digest appears after the attributes */
+	pols->hash_size = get_unaligned_be16(&ctx->pub[8]);
+
+	return ret;
+}
+
+int tpm2_generate_policy_digest(struct tpm2_policies *pols,
+				u32 hash, u8 *policydigest, u32 *plen)
+{
+	int i;
+	struct crypto_shash *tfm;
+	int rc;
+
+	if (pols->count == 0)
+		return 0;
+
+	tfm = crypto_alloc_shash(hash_algo_name[hash], 0, 0);
+	if (IS_ERR(tfm))
+		return PTR_ERR(tfm);
+
+	rc = crypto_shash_digestsize(tfm);
+	if (WARN(rc > MAX_DIGEST_SIZE,
+		 "BUG: trusted key code has alg %s with digest too large (%d)",
+		 hash_algo_name[hash], rc)) {
+		rc = -EINVAL;
+		goto err;
+	}
+	pols->hash = hash;
+	pols->hash_size = rc;
+	*plen = rc;
+
+	/* policy digests always start out all zeros */
+	memset(policydigest, 0, rc);
+
+	for (i = 0; i < pols->count; i++) {
+		u8 *policy = pols->policies[i];
+		int len = pols->len[i];
+		u32 cmd = pols->code[i];
+		u8 digest[MAX_DIGEST_SIZE];
+		u8 code[4];
+		SHASH_DESC_ON_STACK(sdesc, tfm);
+
+		sdesc->tfm = tfm;
+		rc = crypto_shash_init(sdesc);
+		if (rc)
+			goto err;
+
+		/* first hash the previous digest */
+		crypto_shash_update(sdesc, policydigest, *plen);
+		/* then hash the command code */
+		put_unaligned_be32(cmd, code);
+		crypto_shash_update(sdesc, code, 4);
+
+		/* commands that need special handling */
+		if (cmd == TPM2_CC_POLICY_COUNTER_TIMER) {
+			SHASH_DESC_ON_STACK(sdesc1, tfm);
+
+			sdesc1->tfm = tfm;
+
+			/* counter timer policies are double hashed */
+			crypto_shash_digest(sdesc1, policy, len,
+					    digest);
+			policy = digest;
+			len = *plen;
+		}
+		crypto_shash_update(sdesc, policy, len);
+		/* now output the intermediate to the policydigest */
+		crypto_shash_final(sdesc, policydigest);
+
+	}
+	rc = 0;
+
+ err:
+	crypto_free_shash(tfm);
+	return rc;
+}
+
+int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len)
+{
+	const int SCRATCH_SIZE = PAGE_SIZE;
+	u8 *buf = kmalloc(2 * SCRATCH_SIZE, GFP_KERNEL);
+	u8 *work = buf + SCRATCH_SIZE, *ptr;
+	int i;
+
+	if (!buf)
+		return -ENOMEM;
+
+	for (i = 0; i < pols->count; i++) {
+		u8 *seq, *tag;
+		u32 cmd = pols->code[i];
+
+		if (WARN(work - buf + 14 + pols->len[i] > 2 * SCRATCH_SIZE,
+			 "BUG: scratch buffer is too small"))
+			return -EINVAL;
+
+		asn1_encode_sequence(&work, NULL, -1);
+		seq = work;
+
+		asn1_encode_tag(&work, 0, NULL, -1);
+		tag = work;
+		asn1_encode_integer(&work, cmd,
+				    work - buf + SCRATCH_SIZE);
+		asn1_encode_tag(&tag, 0, NULL, work - tag);
+
+		asn1_encode_tag(&work, 1, NULL, -1);
+		tag = work;
+		asn1_encode_octet_string(&work, pols->policies[i],
+					 pols->len[i]);
+		asn1_encode_tag(&tag, 1, NULL, work - tag);
+
+		asn1_encode_sequence(&seq, NULL, work - seq);
+	}
+	ptr = buf;
+	asn1_encode_sequence(&ptr, buf + PAGE_SIZE, work - buf - PAGE_SIZE);
+	*data = buf;
+	*len = ptr - buf;
+
+	return 0;
+}
+
+int tpm2_start_policy_session(struct tpm_chip *chip, u16 hash, u32 *handle)
+{
+	struct tpm_buf buf;
+	int rc;
+	int i;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
+	if (rc)
+		return rc;
+
+	/* NULL salt key handle */
+	tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+	/* NULL bind key handle */
+	tpm_buf_append_u32(&buf, TPM2_RH_NULL);
+	/* empty nonce caller */
+	tpm_buf_append_u16(&buf, 20);
+	for (i = 0; i < 20; i++)
+		tpm_buf_append_u8(&buf, 0);
+	/* empty auth */
+	tpm_buf_append_u16(&buf, 0);
+	/* session type policy */
+	tpm_buf_append_u8(&buf, 0x01);
+
+	/* symmetric encryption parameters */
+	/* symmetric algorithm  */
+	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
+	/* hash algorithm for session */
+	tpm_buf_append_u16(&buf, hash);
+
+	rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+	if (rc)
+		goto out;
+
+	*handle = get_unaligned_be32(buf.data + TPM_HEADER_SIZE);
+ out:
+	tpm_buf_destroy(&buf);
+
+	return rc <= 0 ? rc : -EPERM;
+}
+
+int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
+			    u32 *handle)
+{
+	int i, rc;
+	const char *failure;
+
+	rc = tpm2_start_policy_session(chip, pols->hash, handle);
+	if (rc)
+		return rc;
+
+	for (i = 0; i < pols->count; i++) {
+		u32 cmd = pols->code[i];
+		struct tpm_buf buf;
+
+		rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, cmd);
+		if (rc)
+			return rc;
+
+		tpm_buf_append_u32(&buf, *handle);
+
+		switch (cmd) {
+		case TPM2_CC_POLICY_PCR:
+			failure = "PCR";
+			/*
+			 * for reasons best known to the TCG we have
+			 * to reverse the two arguments to send to the
+			 * policy command
+			 */
+			tpm_buf_append_u16(&buf, pols->hash_size);
+			tpm_buf_append(&buf, pols->policies[i] + pols->len[i] -
+				       pols->hash_size, pols->hash_size);
+			tpm_buf_append(&buf, pols->policies[i],
+				       pols->len[i] - pols->hash_size);
+			break;
+		default:
+			failure = "unknown policy";
+			break;
+		}
+		rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+		tpm_buf_destroy(&buf);
+		if (rc) {
+			printk(KERN_NOTICE "TPM policy %s failed, rc=%d\n",
+			       failure, rc);
+			tpm2_flush_context(chip, *handle);
+			*handle = 0;
+			return -EPERM;
+		}
+	}
+	return 0;
+}
diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
new file mode 100644
index 000000000000..152c948743f3
--- /dev/null
+++ b/security/keys/trusted-keys/tpm2-policy.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+struct tpm2key_context {
+	u32 parent;
+	const u8 *pub;
+	u32 pub_len;
+	const u8 *priv;
+	u32 priv_len;
+	const u8 *policies[TPM2_MAX_POLICIES];
+	u32 policy_code[TPM2_MAX_POLICIES];
+	u16 policy_len[TPM2_MAX_POLICIES];
+	u8 policy_count;
+};
+
+struct tpm2_policies {
+	u32 code[TPM2_MAX_POLICIES];
+	u8 *policies[TPM2_MAX_POLICIES];
+	u16 len[TPM2_MAX_POLICIES];
+	u8 count;
+	u16 hash;
+	u16 hash_size;
+};
+
+int tpmkey_policy_process(struct tpm2key_context *ctx,
+			  struct trusted_key_payload *payload);
+int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
+				u8 *policydigest, u32 *plen);
+int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
+int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
+			    u32 *handle);
diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1
index 1851b7c80f08..f930fd812db3 100644
--- a/security/keys/trusted-keys/tpm2key.asn1
+++ b/security/keys/trusted-keys/tpm2key.asn1
@@ -18,6 +18,6 @@ TPMKey ::= SEQUENCE {
 TPMPolicySequence ::= SEQUENCE OF TPMPolicy
 
 TPMPolicy ::= SEQUENCE {
-	commandCode		[0] EXPLICIT INTEGER,
-	commandPolicy		[1] EXPLICIT OCTET STRING
+	commandCode		[0] EXPLICIT INTEGER ({tpmkey_code}),
+	commandPolicy		[1] EXPLICIT OCTET STRING ({tpmkey_policy})
 	}
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index d744a0d1cb89..6290e611b632 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -707,8 +707,6 @@ enum {
 	Opt_keyhandle, Opt_keyauth, Opt_blobauth,
 	Opt_pcrinfo, Opt_pcrlock, Opt_migratable,
 	Opt_hash,
-	Opt_policydigest,
-	Opt_policyhandle,
 };
 
 static const match_table_t key_tokens = {
@@ -722,8 +720,6 @@ static const match_table_t key_tokens = {
 	{Opt_pcrlock, "pcrlock=%s"},
 	{Opt_migratable, "migratable=%s"},
 	{Opt_hash, "hash=%s"},
-	{Opt_policydigest, "policydigest=%s"},
-	{Opt_policyhandle, "policyhandle=%s"},
 	{Opt_err, NULL}
 };
 
@@ -738,7 +734,6 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 	unsigned long handle;
 	unsigned long lock;
 	unsigned long token_mask = 0;
-	unsigned int digest_len;
 	int i;
 	int tpm2;
 
@@ -801,8 +796,6 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 			opt->pcrlock = lock;
 			break;
 		case Opt_hash:
-			if (test_bit(Opt_policydigest, &token_mask))
-				return -EINVAL;
 			for (i = 0; i < HASH_ALGO__LAST; i++) {
 				if (!strcmp(args[0].from, hash_algo_name[i])) {
 					opt->hash = i;
@@ -816,24 +809,6 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 				return -EINVAL;
 			}
 			break;
-		case Opt_policydigest:
-			digest_len = hash_digest_size[opt->hash];
-			if (!tpm2 || strlen(args[0].from) != (2 * digest_len))
-				return -EINVAL;
-			res = hex2bin(opt->policydigest, args[0].from,
-				      digest_len);
-			if (res < 0)
-				return -EINVAL;
-			opt->policydigest_len = digest_len;
-			break;
-		case Opt_policyhandle:
-			if (!tpm2)
-				return -EINVAL;
-			res = kstrtoul(args[0].from, 16, &handle);
-			if (res < 0)
-				return -EINVAL;
-			opt->policyhandle = handle;
-			break;
 		default:
 			return -EINVAL;
 		}
@@ -1045,6 +1020,7 @@ static void trusted_rcu_free(struct rcu_head *rcu)
 	struct trusted_key_payload *p;
 
 	p = container_of(rcu, struct trusted_key_payload, rcu);
+	kzfree(p->policies);
 	kzfree(p);
 }
 
@@ -1164,7 +1140,11 @@ static long trusted_read(const struct key *key, char __user *buffer,
  */
 static void trusted_destroy(struct key *key)
 {
-	kzfree(key->payload.data[0]);
+	struct trusted_key_payload *p;
+
+	p = key->payload.data[0];
+	kzfree(p->policies);
+	kzfree(p);
 }
 
 struct key_type key_type_trusted = {
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 6d2c5adbff18..ffdd5bf27ea7 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -17,6 +17,7 @@
 #include <asm/unaligned.h>
 
 #include "tpm2key.asn1.h"
+#include "tpm2-policy.h"
 
 static struct tpm2_hash tpm2_hash_map[] = {
 	{HASH_ALGO_SHA1, TPM_ALG_SHA1},
@@ -56,17 +57,34 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 		asn1_encode_boolean(&w, true);
 		asn1_encode_tag(&work, 0, bool, w - bool);
 	}
-	asn1_encode_integer(&work, options->keyhandle,
-			    work - scratch + SCRATCH_SIZE);
+	if (payload->policies) {
+		u8 *encoded_pols;
+		u32 encoded_pol_len;
+		int ret;
+
+		ret = tpm2_encode_policy(payload->policies, &encoded_pols,
+					 &encoded_pol_len);
+
+		if (ret) {
+			return ret;
+		} else {
+			asn1_encode_tag(&work, 1, encoded_pols,
+					encoded_pol_len);
+			kfree(encoded_pols);
+		}
+	}
 	/*
 	 * Assume both ovtet strings will encode to a 2 byte definite length
 	 *
 	 * Note: For a well behaved TPM, this warning should never
 	 * trigger, so if it does there's something nefarious going on
 	 */
-	if (WARN(work - scratch + pub_len + priv_len + 8 > SCRATCH_SIZE,
+	if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE,
 		 "BUG: scratch buffer is too small"))
 		return -EINVAL;
+
+	asn1_encode_integer(&work, options->keyhandle,
+			    SCRATCH_SIZE - (work - scratch));
 	asn1_encode_octet_string(&work, pub, pub_len);
 	asn1_encode_octet_string(&work, priv, priv_len);
 
@@ -76,14 +94,6 @@ static int tpm2_key_encode(struct trusted_key_payload *payload,
 	return work1 - payload->blob;
 }
 
-struct tpm2key_context {
-	u32 parent;
-	const u8 *pub;
-	u32 pub_len;
-	const u8 *priv;
-	u32 priv_len;
-};
-
 static int tpm2_key_decode(struct trusted_key_payload *payload,
 			   struct trusted_key_options *options,
 			   u8 **buf)
@@ -92,6 +102,8 @@ static int tpm2_key_decode(struct trusted_key_payload *payload,
 	struct tpm2key_context ctx;
 	u8 *blob;
 
+	memset(&ctx, 0, sizeof(ctx));
+
 	ret = asn1_ber_decoder(&tpm2key_decoder, &ctx, payload->blob,
 			       payload->blob_len);
 	if (ret < 0)
@@ -104,6 +116,12 @@ static int tpm2_key_decode(struct trusted_key_payload *payload,
 	if (!blob)
 		return -ENOMEM;
 
+	ret = tpmkey_policy_process(&ctx, payload);
+	if (ret) {
+		kfree(blob);
+		return ret;
+	}
+
 	*buf = blob;
 	options->keyhandle = ctx.parent;
 	put_unaligned_be16(ctx.priv_len, blob);
@@ -235,6 +253,37 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (!options->keyhandle)
 		return -EINVAL;
 
+	if (options->pcrinfo_len != 0) {
+		struct tpm2_policies *pols;
+		static u8 *scratch;
+		/* 4 array len, 2 hash alg */
+		const int len = 4 + 2 + options->pcrinfo_len;
+
+		pols = kmalloc(sizeof(*pols) + len, GFP_KERNEL);
+		if (!pols)
+			return -ENOMEM;
+
+		pols->count = 1;
+		pols->len[0] = len;
+		scratch = (u8 *)(pols + 1);
+		pols->policies[0] = scratch;
+		pols->code[0] = TPM2_CC_POLICY_PCR;
+
+		put_unaligned_be32(1, &scratch[0]);
+		put_unaligned_be16(hash, &scratch[4]);
+		memcpy(&scratch[6], options->pcrinfo, options->pcrinfo_len);
+		payload->policies = pols;
+	}
+
+	if (payload->policies) {
+		rc = tpm2_generate_policy_digest(payload->policies,
+						 options->hash,
+						 options->policydigest,
+						 &options->policydigest_len);
+		if (rc)
+			return rc;
+	}
+
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
 	if (rc)
 		return rc;
@@ -438,21 +487,30 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	u16 data_len;
 	u8 *data;
 	int rc;
+	u32 policyhandle = 0;
 
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
 	if (rc)
 		return rc;
 
+	if (payload->policies) {
+		rc = tpm2_get_policy_session(chip, payload->policies,
+					     &policyhandle);
+		if (rc)
+			return rc;
+	}
+
 	tpm_buf_append_u32(&buf, blob_handle);
 	tpm2_buf_append_auth(&buf,
-			     options->policyhandle ?
-			     options->policyhandle : TPM2_RS_PW,
+			     policyhandle ?
+			     policyhandle : TPM2_RS_PW,
 			     NULL /* nonce */, 0,
 			     TPM2_SA_CONTINUE_SESSION,
 			     options->blobauth /* hmac */,
-			     TPM_DIGEST_SIZE);
+			     policyhandle ? 0 : TPM_DIGEST_SIZE);
 
 	rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
+	tpm2_flush_context(chip, policyhandle);
 	if (rc > 0)
 		rc = -EPERM;
 
-- 
2.16.4

[PATCH v2 7/8] security: keys: trusted: add ability to specify arbitrary policy

[James Bottomley]

This patch adds a policy= argument to key creation.  The policy is the
standard tss policymaker format and each separate policy line must
have a newline after it.

Thus to construct a policy requiring authorized value and pcr 16
locking using a sha256 hash, the policy (policy.txt) file would be two
lines:

0000017F00000001000B03000001303095B49BE85E381E5B20E557E46363EF55B0F43B132C2D8E3DE9AC436656F2
0000016b

This can be inserted into the key with

keyctl add trusted kmk "new 32 policy=`cat policy.txt` keyhandle=0x81000001 hash=sha256" @u

Note that although a few policies work like this, most require special
handling which must be added to the kernel policy construction
routine.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 Documentation/security/keys/trusted-encrypted.rst | 16 ++++++++
 security/keys/trusted-keys/tpm2-policy.c          | 46 +++++++++++++++++++++++
 security/keys/trusted-keys/tpm2-policy.h          |  1 +
 security/keys/trusted-keys/trusted_tpm1.c         | 14 ++++++-
 4 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 1a3ca84ad3cd..ade1a9dc8367 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -70,6 +70,9 @@ Usage::
        hash=         hash algorithm name as a string. For TPM 1.x the only
                      allowed value is sha1. For TPM 2.x the allowed values
                      are sha1, sha256, sha384, sha512 and sm3-256.
+       policy=       specify an arbitrary set of policies.  These must
+                     be in policymaker format with each separate
+                     policy line newline terminated.
 
 "keyctl print" returns an ascii hex copy of the sealed key, which is in standard
 TPM_STORED_DATA format.  The key length for new keys are always in bytes.
@@ -162,6 +165,19 @@ zeros (the value of PCR 16)::
     $ dd if=/dev/zero bs=1 count  2>/dev/null|sha1sum
     6768033e216468247bd031a0a2d9876d79818f8f
 
+You can also specify arbitrary policy in policymaker format, so a two
+value policy (the pcr example above and authvalue) would look like
+this in policymaker format::
+
+    0000017F000000010004030000016768033e216468247bd031a0a2d9876d79818f8f
+    0000016b
+
+This can be placed in a file (say policy.txt) and then added to the key as::
+
+    $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 policy=`cat policy.txt`" @u
+
+The newlines in the file policy.txt will be automatically processed.
+
 Reseal a trusted key under new pcr values::
 
     $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
index 1c70f82ed170..6d69f0300584 100644
--- a/security/keys/trusted-keys/tpm2-policy.c
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -338,3 +338,49 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
 	}
 	return 0;
 }
+
+int tpm2_parse_policies(struct tpm2_policies **ppols, char *str)
+{
+	struct tpm2_policies *pols;
+	char *p;
+	u8 *ptr;
+	int i = 0, left = PAGE_SIZE, res;
+
+	pols = kmalloc(left, GFP_KERNEL);
+	if (!pols)
+		return -ENOMEM;
+
+	ptr = (u8 *)(pols + 1);
+	left -= ptr - (u8 *)pols;
+
+	while ((p = strsep(&str, "\n"))) {
+		if (*p = '\0' || *p = '\n')
+			continue;
+		pols->len[i] = strlen(p)/2;
+		if (pols->len[i] > left) {
+			res = -E2BIG;
+			goto err;
+		}
+		res = hex2bin(ptr, p, pols->len[i]);
+		if (res)
+			goto err;
+		/* get command code and skip past */
+		pols->code[i] = get_unaligned_be32(ptr);
+		pols->policies[i] = ptr + 4;
+		ptr += pols->len[i];
+		left -= pols->len[i];
+		pols->len[i] -= 4;
+		/*
+		 * FIXME: this does leave the code embedded in dead
+		 * regions of the memory, but it's easier than
+		 * hexdumping to a temporary or copying over
+		 */
+		i++;
+	}
+	pols->count = i;
+	*ppols = pols;
+	return 0;
+ err:
+	kfree(pols);
+	return res;
+}
diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
index 152c948743f3..cb804a544ced 100644
--- a/security/keys/trusted-keys/tpm2-policy.h
+++ b/security/keys/trusted-keys/tpm2-policy.h
@@ -28,3 +28,4 @@ int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
 int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
 int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
 			    u32 *handle);
+int tpm2_parse_policies(struct tpm2_policies **ppols, char *str);
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 6290e611b632..ba05c75c3170 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -29,6 +29,8 @@
 
 #include <keys/trusted_tpm.h>
 
+#include "tpm2-policy.h"
+
 static const char hmac_alg[] = "hmac(sha1)";
 static const char hash_alg[] = "sha1";
 static struct tpm_chip *chip;
@@ -706,7 +708,7 @@ enum {
 	Opt_new, Opt_load, Opt_update,
 	Opt_keyhandle, Opt_keyauth, Opt_blobauth,
 	Opt_pcrinfo, Opt_pcrlock, Opt_migratable,
-	Opt_hash,
+	Opt_hash, Opt_policy,
 };
 
 static const match_table_t key_tokens = {
@@ -720,6 +722,7 @@ static const match_table_t key_tokens = {
 	{Opt_pcrlock, "pcrlock=%s"},
 	{Opt_migratable, "migratable=%s"},
 	{Opt_hash, "hash=%s"},
+	{Opt_policy, "policy=%s"},
 	{Opt_err, NULL}
 };
 
@@ -809,6 +812,15 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 				return -EINVAL;
 			}
 			break;
+		case Opt_policy:
+			if (pay->policies)
+				return -EINVAL;
+			if (!tpm2)
+				return -EINVAL;
+			res = tpm2_parse_policies(&pay->policies, args[0].from);
+			if (res)
+				return res;
+			break;
 		default:
 			return -EINVAL;
 		}
-- 
2.16.4

[PATCH v2 7/8] security: keys: trusted: add ability to specify arbitrary policy

[James Bottomley]

This patch adds a policy= argument to key creation.  The policy is the
standard tss policymaker format and each separate policy line must
have a newline after it.

Thus to construct a policy requiring authorized value and pcr 16
locking using a sha256 hash, the policy (policy.txt) file would be two
lines:

0000017F00000001000B03000001303095B49BE85E381E5B20E557E46363EF55B0F43B132C2D8E3DE9AC436656F2
0000016b

This can be inserted into the key with

keyctl add trusted kmk "new 32 policy=`cat policy.txt` keyhandle=0x81000001 hash=sha256" @u

Note that although a few policies work like this, most require special
handling which must be added to the kernel policy construction
routine.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 Documentation/security/keys/trusted-encrypted.rst | 16 ++++++++
 security/keys/trusted-keys/tpm2-policy.c          | 46 +++++++++++++++++++++++
 security/keys/trusted-keys/tpm2-policy.h          |  1 +
 security/keys/trusted-keys/trusted_tpm1.c         | 14 ++++++-
 4 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 1a3ca84ad3cd..ade1a9dc8367 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -70,6 +70,9 @@ Usage::
        hash=         hash algorithm name as a string. For TPM 1.x the only
                      allowed value is sha1. For TPM 2.x the allowed values
                      are sha1, sha256, sha384, sha512 and sm3-256.
+       policy=       specify an arbitrary set of policies.  These must
+                     be in policymaker format with each separate
+                     policy line newline terminated.
 
 "keyctl print" returns an ascii hex copy of the sealed key, which is in standard
 TPM_STORED_DATA format.  The key length for new keys are always in bytes.
@@ -162,6 +165,19 @@ zeros (the value of PCR 16)::
     $ dd if=/dev/zero bs=1 count=20 2>/dev/null|sha1sum
     6768033e216468247bd031a0a2d9876d79818f8f
 
+You can also specify arbitrary policy in policymaker format, so a two
+value policy (the pcr example above and authvalue) would look like
+this in policymaker format::
+
+    0000017F000000010004030000016768033e216468247bd031a0a2d9876d79818f8f
+    0000016b
+
+This can be placed in a file (say policy.txt) and then added to the key as::
+
+    $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 policy=`cat policy.txt`" @u
+
+The newlines in the file policy.txt will be automatically processed.
+
 Reseal a trusted key under new pcr values::
 
     $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
index 1c70f82ed170..6d69f0300584 100644
--- a/security/keys/trusted-keys/tpm2-policy.c
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -338,3 +338,49 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
 	}
 	return 0;
 }
+
+int tpm2_parse_policies(struct tpm2_policies **ppols, char *str)
+{
+	struct tpm2_policies *pols;
+	char *p;
+	u8 *ptr;
+	int i = 0, left = PAGE_SIZE, res;
+
+	pols = kmalloc(left, GFP_KERNEL);
+	if (!pols)
+		return -ENOMEM;
+
+	ptr = (u8 *)(pols + 1);
+	left -= ptr - (u8 *)pols;
+
+	while ((p = strsep(&str, "\n"))) {
+		if (*p == '\0' || *p == '\n')
+			continue;
+		pols->len[i] = strlen(p)/2;
+		if (pols->len[i] > left) {
+			res = -E2BIG;
+			goto err;
+		}
+		res = hex2bin(ptr, p, pols->len[i]);
+		if (res)
+			goto err;
+		/* get command code and skip past */
+		pols->code[i] = get_unaligned_be32(ptr);
+		pols->policies[i] = ptr + 4;
+		ptr += pols->len[i];
+		left -= pols->len[i];
+		pols->len[i] -= 4;
+		/*
+		 * FIXME: this does leave the code embedded in dead
+		 * regions of the memory, but it's easier than
+		 * hexdumping to a temporary or copying over
+		 */
+		i++;
+	}
+	pols->count = i;
+	*ppols = pols;
+	return 0;
+ err:
+	kfree(pols);
+	return res;
+}
diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
index 152c948743f3..cb804a544ced 100644
--- a/security/keys/trusted-keys/tpm2-policy.h
+++ b/security/keys/trusted-keys/tpm2-policy.h
@@ -28,3 +28,4 @@ int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
 int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
 int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
 			    u32 *handle);
+int tpm2_parse_policies(struct tpm2_policies **ppols, char *str);
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 6290e611b632..ba05c75c3170 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -29,6 +29,8 @@
 
 #include <keys/trusted_tpm.h>
 
+#include "tpm2-policy.h"
+
 static const char hmac_alg[] = "hmac(sha1)";
 static const char hash_alg[] = "sha1";
 static struct tpm_chip *chip;
@@ -706,7 +708,7 @@ enum {
 	Opt_new, Opt_load, Opt_update,
 	Opt_keyhandle, Opt_keyauth, Opt_blobauth,
 	Opt_pcrinfo, Opt_pcrlock, Opt_migratable,
-	Opt_hash,
+	Opt_hash, Opt_policy,
 };
 
 static const match_table_t key_tokens = {
@@ -720,6 +722,7 @@ static const match_table_t key_tokens = {
 	{Opt_pcrlock, "pcrlock=%s"},
 	{Opt_migratable, "migratable=%s"},
 	{Opt_hash, "hash=%s"},
+	{Opt_policy, "policy=%s"},
 	{Opt_err, NULL}
 };
 
@@ -809,6 +812,15 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
 				return -EINVAL;
 			}
 			break;
+		case Opt_policy:
+			if (pay->policies)
+				return -EINVAL;
+			if (!tpm2)
+				return -EINVAL;
+			res = tpm2_parse_policies(&pay->policies, args[0].from);
+			if (res)
+				return res;
+			break;
 		default:
 			return -EINVAL;
 		}
-- 
2.16.4

[PATCH v2 8/8] security: keys: trusted: implement counter/timer policy

[James Bottomley]

This is actually a generic policy allowing a range of comparisons
against any value set in the TPM Clock, which includes things like the
reset count, a monotonic millisecond count and the restart count.  The
most useful comparison is against the millisecond count for expiring
keys.  However, you have to remember that currently Linux doesn't try
to sync the epoch timer with the TPM, so the expiration is actually
measured in how long the TPM itself has been powered on ... the TPM
timer doesn't count while the system is powered down.  The millisecond
counter is a u64 quantity found at offset 8 in the timer structure,
and the <= comparision operand is 9, so a policy set to expire after the
TPM has been up for 100 seconds would look like

0000016d00000000000f424000080009

Where 0x16d is the counter timer policy code and 0xf4240 is 100 000 in
hex.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 Documentation/security/keys/trusted-encrypted.rst | 29 +++++++++++++++++++++++
 security/keys/trusted-keys/tpm2-policy.c          | 19 +++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index ade1a9dc8367..52d8bd8bef65 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -235,3 +235,32 @@ about the usage can be found in the file
 Another new format 'enc32' has been defined in order to support encrypted keys
 with payload size of 32 bytes. This will initially be used for nvdimm security
 but may expand to other usages that require 32 bytes payload.
+
+Appendix
+--------
+
+TPM 2.0 Policies
+----------------
+
+The current TPM supports PCR lock policies as documented above and
+CounterTimer policies which can be used to create expiring keys.  One
+caveat with expiring keys is that the TPM millisecond counter does not
+update while a system is powered off and Linux does not sync the TPM
+millisecond count with its internal clock, so the best you can expire
+in is in terms of how long any given TPM has been powered on.  (FIXME:
+Linux should simply update the millisecond clock to the current number
+of seconds past the epoch on boot).
+
+A CounterTimer policy is expressed in terms of length and offset
+against the TPM clock structure (TPMS_TIME_INFO), which looks like the
+packed structure::
+
+    struct tpms_time_info {
+            u64 uptime;       /* time in ms since last start or reset */
+	    u64 clock;        /* cumulative uptime in ms */
+	    u32 resetcount;   /* numer of times the TPM has been reset */
+	    u32 restartcount; /* number of times the TPM has been restarted */
+	    u8  safe          /* time was safely loaded from NVRam */
+    };
+
+The usual comparison for expiring keys is against clock, at offset 8.
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
index 6d69f0300584..f19beb3e9e49 100644
--- a/security/keys/trusted-keys/tpm2-policy.c
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -322,6 +322,25 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
 			tpm_buf_append(&buf, pols->policies[i],
 				       pols->len[i] - pols->hash_size);
 			break;
+		case TPM2_CC_POLICY_COUNTER_TIMER: {
+			/*
+			 * the format of this is the last two u16
+			 * quantities are the offset and operation
+			 * respectively.  The rest is operandB which
+			 * must be zero padded in a hash digest
+			 */
+			u16 opb_len = pols->len[i] - 4;
+
+			if (opb_len > pols->hash_size)
+				return -EINVAL;
+
+			tpm_buf_append_u16(&buf, opb_len);
+			tpm_buf_append(&buf, pols->policies[i], opb_len);
+			/* offset and operand*/
+			tpm_buf_append(&buf, pols->policies[i] + opb_len, 4);
+			failure = "Counter Timer";
+			break;
+		}
 		default:
 			failure = "unknown policy";
 			break;
-- 
2.16.4

[PATCH v2 8/8] security: keys: trusted: implement counter/timer policy

[James Bottomley]

This is actually a generic policy allowing a range of comparisons
against any value set in the TPM Clock, which includes things like the
reset count, a monotonic millisecond count and the restart count.  The
most useful comparison is against the millisecond count for expiring
keys.  However, you have to remember that currently Linux doesn't try
to sync the epoch timer with the TPM, so the expiration is actually
measured in how long the TPM itself has been powered on ... the TPM
timer doesn't count while the system is powered down.  The millisecond
counter is a u64 quantity found at offset 8 in the timer structure,
and the <= comparision operand is 9, so a policy set to expire after the
TPM has been up for 100 seconds would look like

0000016d00000000000f424000080009

Where 0x16d is the counter timer policy code and 0xf4240 is 100 000 in
hex.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 Documentation/security/keys/trusted-encrypted.rst | 29 +++++++++++++++++++++++
 security/keys/trusted-keys/tpm2-policy.c          | 19 +++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index ade1a9dc8367..52d8bd8bef65 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -235,3 +235,32 @@ about the usage can be found in the file
 Another new format 'enc32' has been defined in order to support encrypted keys
 with payload size of 32 bytes. This will initially be used for nvdimm security
 but may expand to other usages that require 32 bytes payload.
+
+Appendix
+--------
+
+TPM 2.0 Policies
+----------------
+
+The current TPM supports PCR lock policies as documented above and
+CounterTimer policies which can be used to create expiring keys.  One
+caveat with expiring keys is that the TPM millisecond counter does not
+update while a system is powered off and Linux does not sync the TPM
+millisecond count with its internal clock, so the best you can expire
+in is in terms of how long any given TPM has been powered on.  (FIXME:
+Linux should simply update the millisecond clock to the current number
+of seconds past the epoch on boot).
+
+A CounterTimer policy is expressed in terms of length and offset
+against the TPM clock structure (TPMS_TIME_INFO), which looks like the
+packed structure::
+
+    struct tpms_time_info {
+            u64 uptime;       /* time in ms since last start or reset */
+	    u64 clock;        /* cumulative uptime in ms */
+	    u32 resetcount;   /* numer of times the TPM has been reset */
+	    u32 restartcount; /* number of times the TPM has been restarted */
+	    u8  safe          /* time was safely loaded from NVRam */
+    };
+
+The usual comparison for expiring keys is against clock, at offset 8.
diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
index 6d69f0300584..f19beb3e9e49 100644
--- a/security/keys/trusted-keys/tpm2-policy.c
+++ b/security/keys/trusted-keys/tpm2-policy.c
@@ -322,6 +322,25 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols,
 			tpm_buf_append(&buf, pols->policies[i],
 				       pols->len[i] - pols->hash_size);
 			break;
+		case TPM2_CC_POLICY_COUNTER_TIMER: {
+			/*
+			 * the format of this is the last two u16
+			 * quantities are the offset and operation
+			 * respectively.  The rest is operandB which
+			 * must be zero padded in a hash digest
+			 */
+			u16 opb_len = pols->len[i] - 4;
+
+			if (opb_len > pols->hash_size)
+				return -EINVAL;
+
+			tpm_buf_append_u16(&buf, opb_len);
+			tpm_buf_append(&buf, pols->policies[i], opb_len);
+			/* offset and operand*/
+			tpm_buf_append(&buf, pols->policies[i] + opb_len, 4);
+			failure = "Counter Timer";
+			break;
+		}
 		default:
 			failure = "unknown policy";
 			break;
-- 
2.16.4

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[David Woodhouse]

[-- Attachment #1: Type: text/plain, Size: 2226 bytes --]

On Mon, 2019-12-09 at 16:06 -0800, James Bottomley wrote:
> +/**
> + * asn1_encode_integer - encode positive integer to ASN.1
> + * @_data: pointer to the pointer to the data
> + * @integer: integer to be encoded
> + * @len: length of buffer
> + *
> + * This is a simplified encoder: it only currently does
> + * positive integers, but it should be simple enough to add the 
> + * negative case if a use comes along.
> + */
> +void asn1_encode_integer(unsigned char **_data, s64 integer, int len)
> +{
> +       unsigned char *data = *_data, *d = &data[2];
> +       int i;
> +       bool found = false;
> +
> +       if (WARN(integer < 0,
> +                "BUG: asn1_encode_integer only supports positive integers"))
> +               return;
> +
> +       if (WARN(len < 3,
> +                "BUG: buffer for integers must have at least 3 bytes"))
> +               return;
> +
> +       len =- 2;
> +
> +       data[0] = _tag(UNIV, PRIM, INT);
> +       if (integer == 0) {
> +               *d++ = 0;
> +               goto out;
> +       }
> +       for (i = sizeof(integer); i > 0 ; i--) {
> +               int byte = integer >> (8*(i-1));
> +
> +               if (!found && byte == 0)
> +                       continue;
> +               found = true;
> +               if (byte & 0x80) {
> +                       /*
> +                        * no check needed here, we already know we
> +                        * have len >= 1
> +                        */
> +                       *d++ = 0;
> +                       len--;
> +               }
> +               if (WARN(len == 0,
> +                        "BUG buffer too short in asn1_encode_integer"))
> +                       return;
> +               *d++ = byte;
> +               len--;
> +       }
> + out:
> +       data[1] = d - data - 2;
> +       *_data = d;
> +}
> +EXPORT_SYMBOL_GPL(asn1_encode_integer);


Didn't you say you were going to make it return an error when it ran
out of space or was asked to encode a negative number?

There are other encoding functions which you haven't yet added the
buffer length field to, and they'll want to be able to return -ENOSPC
too.


[-- Attachment #2: smime.p7s --]
[-- Type: application/x-pkcs7-signature, Size: 5174 bytes --]

Re: [PATCH v2 3/8] oid_registry: Add TCG defined OIDS for TPM keys

[David Woodhouse]

[-- Attachment #1: Type: text/plain, Size: 324 bytes --]

On Mon, 2019-12-09 at 16:06 -0800, James Bottomley wrote:
> +       /* TCG defined OIDS for TPM based keys */
> +       OID_TPMLoadableKey,             /* 2.23.133.10.1.3 */
> +       OID_TPMImporableKey,            /* 2.23.133.10.1.4 */


There's a t missing from OID_TPMImpoTableKey. Sorry, missed that last
time.

[-- Attachment #2: smime.p7s --]
[-- Type: application/x-pkcs7-signature, Size: 5174 bytes --]

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Tue, 2019-12-10 at 08:18 +0000, David Woodhouse wrote:
> On Mon, 2019-12-09 at 16:06 -0800, James Bottomley wrote:
> > +/**
> > + * asn1_encode_integer - encode positive integer to ASN.1
> > + * @_data: pointer to the pointer to the data
> > + * @integer: integer to be encoded
> > + * @len: length of buffer
> > + *
> > + * This is a simplified encoder: it only currently does
> > + * positive integers, but it should be simple enough to add the 
> > + * negative case if a use comes along.
> > + */
> > +void asn1_encode_integer(unsigned char **_data, s64 integer, int
> > len)
> > +{
> > +       unsigned char *data = *_data, *d = &data[2];
> > +       int i;
> > +       bool found = false;
> > +
> > +       if (WARN(integer < 0,
> > +                "BUG: asn1_encode_integer only supports positive
> > integers"))
> > +               return;
> > +
> > +       if (WARN(len < 3,
> > +                "BUG: buffer for integers must have at least 3
> > bytes"))
> > +               return;
> > +
> > +       len =- 2;
> > +
> > +       data[0] = _tag(UNIV, PRIM, INT);
> > +       if (integer = 0) {
> > +               *d++ = 0;
> > +               goto out;
> > +       }
> > +       for (i = sizeof(integer); i > 0 ; i--) {
> > +               int byte = integer >> (8*(i-1));
> > +
> > +               if (!found && byte = 0)
> > +                       continue;
> > +               found = true;
> > +               if (byte & 0x80) {
> > +                       /*
> > +                        * no check needed here, we already know we
> > +                        * have len >= 1
> > +                        */
> > +                       *d++ = 0;
> > +                       len--;
> > +               }
> > +               if (WARN(len = 0,
> > +                        "BUG buffer too short in
> > asn1_encode_integer"))
> > +                       return;
> > +               *d++ = byte;
> > +               len--;
> > +       }
> > + out:
> > +       data[1] = d - data - 2;
> > +       *_data = d;
> > +}
> > +EXPORT_SYMBOL_GPL(asn1_encode_integer);
> 
> 
> Didn't you say you were going to make it return an error when it ran
> out of space or was asked to encode a negative number?

it follows the pattern of all the other functions in that it dumps a
kernel warning on problems and bails.  I don't really want to add error
handling for my use case, since it's not expected to have any problems.
 My main problem case is a malicious user tricking the kernel into
trying to overflow the output buffer and in that case I don't really
care that the ASN.1 output will be malformed as long as the buffer
doesn't overflow.

James

> There are other encoding functions which you haven't yet added the
> buffer length field to, and they'll want to be able to return -ENOSPC
> too.

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Tue, 2019-12-10 at 08:18 +0000, David Woodhouse wrote:
> On Mon, 2019-12-09 at 16:06 -0800, James Bottomley wrote:
> > +/**
> > + * asn1_encode_integer - encode positive integer to ASN.1
> > + * @_data: pointer to the pointer to the data
> > + * @integer: integer to be encoded
> > + * @len: length of buffer
> > + *
> > + * This is a simplified encoder: it only currently does
> > + * positive integers, but it should be simple enough to add the 
> > + * negative case if a use comes along.
> > + */
> > +void asn1_encode_integer(unsigned char **_data, s64 integer, int
> > len)
> > +{
> > +       unsigned char *data = *_data, *d = &data[2];
> > +       int i;
> > +       bool found = false;
> > +
> > +       if (WARN(integer < 0,
> > +                "BUG: asn1_encode_integer only supports positive
> > integers"))
> > +               return;
> > +
> > +       if (WARN(len < 3,
> > +                "BUG: buffer for integers must have at least 3
> > bytes"))
> > +               return;
> > +
> > +       len =- 2;
> > +
> > +       data[0] = _tag(UNIV, PRIM, INT);
> > +       if (integer == 0) {
> > +               *d++ = 0;
> > +               goto out;
> > +       }
> > +       for (i = sizeof(integer); i > 0 ; i--) {
> > +               int byte = integer >> (8*(i-1));
> > +
> > +               if (!found && byte == 0)
> > +                       continue;
> > +               found = true;
> > +               if (byte & 0x80) {
> > +                       /*
> > +                        * no check needed here, we already know we
> > +                        * have len >= 1
> > +                        */
> > +                       *d++ = 0;
> > +                       len--;
> > +               }
> > +               if (WARN(len == 0,
> > +                        "BUG buffer too short in
> > asn1_encode_integer"))
> > +                       return;
> > +               *d++ = byte;
> > +               len--;
> > +       }
> > + out:
> > +       data[1] = d - data - 2;
> > +       *_data = d;
> > +}
> > +EXPORT_SYMBOL_GPL(asn1_encode_integer);
> 
> 
> Didn't you say you were going to make it return an error when it ran
> out of space or was asked to encode a negative number?

it follows the pattern of all the other functions in that it dumps a
kernel warning on problems and bails.  I don't really want to add error
handling for my use case, since it's not expected to have any problems.
 My main problem case is a malicious user tricking the kernel into
trying to overflow the output buffer and in that case I don't really
care that the ASN.1 output will be malformed as long as the buffer
doesn't overflow.

James

> There are other encoding functions which you haven't yet added the
> buffer length field to, and they'll want to be able to return -ENOSPC
> too.

Re: [PATCH v2 3/8] oid_registry: Add TCG defined OIDS for TPM keys

[James Bottomley]

On Tue, 2019-12-10 at 08:18 +0000, David Woodhouse wrote:
> On Mon, 2019-12-09 at 16:06 -0800, James Bottomley wrote:
> > +       /* TCG defined OIDS for TPM based keys */
> > +       OID_TPMLoadableKey,             /* 2.23.133.10.1.3 */
> > +       OID_TPMImporableKey,            /* 2.23.133.10.1.4 */
> 
> 
> There's a t missing from OID_TPMImpoTableKey. Sorry, missed that last
> time.

Heh, yes, will fix.

James

Re: [PATCH v2 3/8] oid_registry: Add TCG defined OIDS for TPM keys

[James Bottomley]

On Tue, 2019-12-10 at 08:18 +0000, David Woodhouse wrote:
> On Mon, 2019-12-09 at 16:06 -0800, James Bottomley wrote:
> > +       /* TCG defined OIDS for TPM based keys */
> > +       OID_TPMLoadableKey,             /* 2.23.133.10.1.3 */
> > +       OID_TPMImporableKey,            /* 2.23.133.10.1.4 */
> 
> 
> There's a t missing from OID_TPMImpoTableKey. Sorry, missed that last
> time.

Heh, yes, will fix.

James

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[David Howells]

James Bottomley <James.Bottomley@HansenPartnership.com> wrote:

> > Didn't you say you were going to make it return an error when it ran
> > out of space or was asked to encode a negative number?
> 
> it follows the pattern of all the other functions in that it dumps a
> kernel warning on problems and bails.

I don't see any bounds checking there, let alone anything that dumps a kernel
warning and bails - except if the length is so large that the ASN.1 cannot be
constructed.  That said, there is a check in patch 4.

> ... as long as the buffer doesn't overflow.

Yes, but that's Dave's point.

[from patch 4]

> +	 * Assume both ovtet strings will encode to a 2 byte definite length

octet, btw.

At least I've found a preliminary bounds check there

> +	 */
> +	if (WARN(work - scratch + pub_len + priv_len + 8 > SCRATCH_SIZE,
> +		 "BUG: scratch buffer is too small"))
> +		return -EINVAL;

which I presume makes the correct calculation.

I thought TPM comms were slow - slow enough that putting bounds checking in
your asn1_encode_* routines will be insignificant.

Further, you're promoting this ASN.1 encoder as a general library within the
kernel, presumably so that other people can make use of it.  Please therefore
put bounds checking and error handling in it.  And please *don't* just produce
broken ASN.1 when something goes wrong.

David

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Tue, 2019-12-10 at 14:08 +0000, David Howells wrote:
> James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> 
> > > Didn't you say you were going to make it return an error when it
> > > ran out of space or was asked to encode a negative number?
> > 
> > it follows the pattern of all the other functions in that it dumps
> > a kernel warning on problems and bails.
> 
> I don't see any bounds checking there, let alone anything that dumps
> a kernel warning and bails 

It's in the if (WARN part of asn1_encode_integer.

> - except if the length is so large that the ASN.1 cannot be
> constructed.  That said, there is a check in patch 4.

However, I think you'd like both a length and a buffer length to each
function to cope with definite length encoding overflows?  I can do
that.

> > ... as long as the buffer doesn't overflow.
> 
> Yes, but that's Dave's point.
> 
> [from patch 4]
> 
> > +	 * Assume both ovtet strings will encode to a 2 byte
> > definite length
> 
> octet, btw.

Heh, yes, noticed that mere seconds after I pressed send ...

> At least I've found a preliminary bounds check there
> 
> > +	 */
> > +	if (WARN(work - scratch + pub_len + priv_len + 8 >
> > SCRATCH_SIZE,
> > +		 "BUG: scratch buffer is too small"))
> > +		return -EINVAL;
> 
> which I presume makes the correct calculation.
> 
> I thought TPM comms were slow - slow enough that putting bounds
> checking in your asn1_encode_* routines will be insignificant.

Yes, I'm not bothered about timings.  I can add bounds checking on the
buffer length like the integer case.  For the other routines, I'll make
it decrement the data length in place as it increments the data pointer

> Further, you're promoting this ASN.1 encoder as a general library
> within the kernel, presumably so that other people can make use of
> it.

Well, I did notice the TPM 1.2 asymmetric key code rolled its own ASN.1
encoding, yes.

>   Please therefore put bounds checking and error handling in it.  And
> please *don't* just produce broken ASN.1 when something goes wrong.

OK, I'll make it return an error and add a wrapper for my use case that
warns on error and causes the function to bail.

James

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Tue, 2019-12-10 at 14:08 +0000, David Howells wrote:
> James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> 
> > > Didn't you say you were going to make it return an error when it
> > > ran out of space or was asked to encode a negative number?
> > 
> > it follows the pattern of all the other functions in that it dumps
> > a kernel warning on problems and bails.
> 
> I don't see any bounds checking there, let alone anything that dumps
> a kernel warning and bails 

It's in the if (WARN part of asn1_encode_integer.

> - except if the length is so large that the ASN.1 cannot be
> constructed.  That said, there is a check in patch 4.

However, I think you'd like both a length and a buffer length to each
function to cope with definite length encoding overflows?  I can do
that.

> > ... as long as the buffer doesn't overflow.
> 
> Yes, but that's Dave's point.
> 
> [from patch 4]
> 
> > +	 * Assume both ovtet strings will encode to a 2 byte
> > definite length
> 
> octet, btw.

Heh, yes, noticed that mere seconds after I pressed send ...

> At least I've found a preliminary bounds check there
> 
> > +	 */
> > +	if (WARN(work - scratch + pub_len + priv_len + 8 >
> > SCRATCH_SIZE,
> > +		 "BUG: scratch buffer is too small"))
> > +		return -EINVAL;
> 
> which I presume makes the correct calculation.
> 
> I thought TPM comms were slow - slow enough that putting bounds
> checking in your asn1_encode_* routines will be insignificant.

Yes, I'm not bothered about timings.  I can add bounds checking on the
buffer length like the integer case.  For the other routines, I'll make
it decrement the data length in place as it increments the data pointer

> Further, you're promoting this ASN.1 encoder as a general library
> within the kernel, presumably so that other people can make use of
> it.

Well, I did notice the TPM 1.2 asymmetric key code rolled its own ASN.1
encoding, yes.

>   Please therefore put bounds checking and error handling in it.  And
> please *don't* just produce broken ASN.1 when something goes wrong.

OK, I'll make it return an error and add a wrapper for my use case that
warns on error and causes the function to bail.

James

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[David Woodhouse]

On 10 December 2019 18:53:40 GMT, James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
>On Tue, 2019-12-10 at 14:08 +0000, David Howells wrote:
>>   Please therefore put bounds checking and error handling in it.  And
>> please *don't* just produce broken ASN.1 when something goes wrong.
>
>OK, I'll make it return an error and add a wrapper for my use case that
>warns on error and causes the function to bail.

Traditionally we call that "error handling" :p

-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Tue, 2019-12-10 at 22:37 +0000, David Woodhouse wrote:
> 
> On 10 December 2019 18:53:40 GMT, James Bottomley <James.Bottomley@Ha
> nsenPartnership.com> wrote:
> > On Tue, 2019-12-10 at 14:08 +0000, David Howells wrote:
> > >   Please therefore put bounds checking and error handling in
> > > it.  And
> > > please *don't* just produce broken ASN.1 when something goes
> > > wrong.
> > 
> > OK, I'll make it return an error and add a wrapper for my use case
> > that
> > warns on error and causes the function to bail.
> 
> Traditionally we call that "error handling" :p

This is what I'm thinking (still reworking the rest of the series ... I
found out that AA doesn't habitually have power sockets and my laptop
dying in the middle of a rebase turned out not to be such a good
thing).

James

---

From 7b0c52cf07ca2b8b8ddbe0442a6d3f9de30f7b1b Mon Sep 17 00:00:00 2001
From: James Bottomley <James.Bottomley@HansenPartnership.com>
Date: Wed, 4 Dec 2019 15:19:01 -0800
Subject: [PATCH] lib: add asn.1 encoder

We have a need in the TPM trusted keys to return the ASN.1 form of the
TPM key blob so it can be operated on by tools outside of the kernel.
To do that, we have to be able to read and write the key format.  The
current ASN.1 decoder does fine for reading, but we need pieces of an
ASN.1 encoder to return the key blob.

The current implementation only encodes the ASN.1 bits we actually need.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: updated API to use indefinite length, and made symbol exports gpl

diff --git a/include/linux/asn1_encoder.h b/include/linux/asn1_encoder.h
new file mode 100644
index 000000000000..f4afe5ad79a8
--- /dev/null
+++ b/include/linux/asn1_encoder.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _LINUX_ASN1_ENCODER_H
+#define _LINUX_ASN1_ENCODER_H
+
+#include <linux/types.h>
+#include <linux/asn1.h>
+#include <linux/asn1_ber_bytecode.h>
+#include <linux/bug.h>
+
+#define asn1_oid_len(oid) (sizeof(oid)/sizeof(u32))
+int asn1_encode_integer(unsigned char **_data, int *data_len,
+			s64 integer);
+int asn1_encode_oid(unsigned char **_data, int *data_len,
+		    u32 oid[], int oid_len);
+int asn1_encode_tag(unsigned char **data, int *data_len, u32 tag,
+		    const unsigned char *string, int len);
+int asn1_encode_octet_string(unsigned char **data, int *data_len,
+			     const unsigned char *string, u32 len);
+int asn1_encode_sequence(unsigned char **data, int *data_len,
+			 const unsigned char *seq, int len);
+int asn1_encode_boolean(unsigned char **data, int *data_len, bool val);
+
+#endif
diff --git a/lib/Makefile b/lib/Makefile
index c2f0e2a4e4e8..515b35f92c3c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -233,7 +233,7 @@ obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o
 
 obj-$(CONFIG_PERCPU_TEST) += percpu_test.o
 
-obj-$(CONFIG_ASN1) += asn1_decoder.o
+obj-$(CONFIG_ASN1) += asn1_decoder.o asn1_encoder.o
 
 obj-$(CONFIG_FONT_SUPPORT) += fonts/
 
diff --git a/lib/asn1_encoder.c b/lib/asn1_encoder.c
new file mode 100644
index 000000000000..c3c03bad7e6a
--- /dev/null
+++ b/lib/asn1_encoder.c
@@ -0,0 +1,362 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Simple encoder primitives for ASN.1 BER/DER/CER
+ *
+ * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
+ */
+
+#include <linux/asn1_encoder.h>
+#include <linux/bug.h>
+#include <linux/string.h>
+#include <linux/module.h>
+
+/**
+ * asn1_encode_integer - encode positive integer to ASN.1
+ * @_data: pointer to the pointer to the data
+ * @data_len: length of buffer remaining
+ * @integer: integer to be encoded
+ *
+ * This is a simplified encoder: it only currently does
+ * positive integers, but it should be simple enough to add the
+ * negative case if a use comes along.
+ */
+int asn1_encode_integer(unsigned char **_data, int *data_len, s64 integer)
+{
+	unsigned char *data = *_data, *d = &data[2];
+	int i;
+	bool found = false;
+
+	if (WARN(integer < 0,
+		 "BUG: integer encode only supports positive integers"))
+		return -EINVAL;
+
+	if (*data_len < 3)
+		return -EINVAL;
+
+	*data_len -= 2;
+
+	data[0] = _tag(UNIV, PRIM, INT);
+	if (integer = 0) {
+		*d++ = 0;
+		goto out;
+	}
+	for (i = sizeof(integer); i > 0 ; i--) {
+		int byte = integer >> (8*(i-1));
+
+		if (!found && byte = 0)
+			continue;
+		found = true;
+		if (byte & 0x80) {
+			/*
+			 * no check needed here, we already know we
+			 * have len >= 1
+			 */
+			*d++ = 0;
+			(*data_len)--;
+		}
+		if (*data_len = 0)
+			return -EINVAL;
+		*d++ = byte;
+		(*data_len)--;
+	}
+ out:
+	data[1] = d - data - 2;
+	*_data = d;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_integer);
+
+/* calculate the base 128 digit values setting the top bit of the first octet */
+static int asn1_encode_oid_digit(unsigned char **_data, int *data_len, u32 oid)
+{
+	int start = 7 + 7 + 7 + 7;
+	unsigned char *data = *_data;
+	int ret = 0;
+
+	if (*data_len < 1)
+		return -EINVAL;
+
+	/* quick case */
+	if (oid = 0) {
+		*data++ = 0x80;
+		(*data_len)--;
+		goto out;
+	}
+
+	while (oid >> start = 0)
+		start -= 7;
+
+	while (start > 0 && *data_len > 0) {
+		u8 byte;
+
+		byte = oid >> start;
+		oid = oid - (byte << start);
+		start -= 7;
+		byte |= 0x80;
+		*data++ = byte;
+		(*data_len)--;
+	}
+	if (*data_len > 0) {
+		*data++ = oid;
+		(*data_len)--;
+	} else {
+		ret = -EINVAL;
+	}
+
+ out:
+	*_data = data;
+	return ret;
+}
+
+/**
+ * asn1_encode_oid - encode an oid to ASN.1
+ * @_data: position to begin encoding at
+ * @data_len: remaining bytes in @_data
+ * @oid: array of oids
+ * @oid_len: length of oid array
+ *
+ * this encodes an OID up to ASN.1 when presented as an array of OID values
+ */
+int asn1_encode_oid(unsigned char **_data, int *data_len,
+		    u32 oid[], int oid_len)
+{
+	unsigned char *data = *_data;
+	unsigned char *d = data + 2;
+	int i, ret;
+
+	if (WARN(oid_len < 2, "OID must have at least two elements"))
+		return -EINVAL;
+	if (WARN(oid_len > 32, "OID is too large"))
+		return -EINVAL;
+	if (*data_len < 2)
+		return -EINVAL;
+
+	data[0] = _tag(UNIV, PRIM, OID);
+	*d++ = oid[0] * 40 + oid[1];
+	*data_len -= 2;
+	ret = 0;
+	for (i = 2; i < oid_len; i++) {
+		ret = asn1_encode_oid_digit(&d, data_len, oid[i]);
+		if (ret < 0)
+			return ret;
+	}
+	data[1] = d - data - 2;
+	*_data = d;
+	return ret;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_oid);
+
+static int asn1_encode_length(unsigned char **data, int *data_len, int len)
+{
+	if (*data_len < 1)
+		return -EINVAL;
+	(*data_len)--;
+	if (len < 0) {
+		*((*data)++) = ASN1_INDEFINITE_LENGTH;
+		return 0;
+	}
+	if (*data_len < 1)
+		return -EINVAL;
+	if (len <= 0x7f) {
+		*((*data)++) = len;
+		(*data_len)--;
+		return 0;
+	}
+
+	if (*data_len < 2)
+		return -EINVAL;
+	if (len <= 0xff) {
+		*((*data)++) = 0x81;
+		*((*data)++) = len & 0xff;
+		*data_len -= 2;
+		return 0;
+	}
+	if (*data_len < 3)
+		return -EINVAL;
+	if (len <= 0xffff) {
+		*((*data)++) = 0x82;
+		*((*data)++) = (len >> 8) & 0xff;
+		*((*data)++) = len & 0xff;
+		*data_len -= 3;
+		return 0;
+	}
+
+	if (WARN(len > 0xffffff, "ASN.1 length can't be > 0xffffff"))
+		return -EINVAL;
+
+	if (*data_len < 4)
+		return -EINVAL;
+	*((*data)++) = 0x83;
+	*((*data)++) = (len >> 16) & 0xff;
+	*((*data)++) = (len >> 8) & 0xff;
+	*((*data)++) = len & 0xff;
+	*data_len -= 4;
+
+	return 0;
+}
+
+/**
+ * asn1_encode_tag - add a tag for optional or explicit value
+ * @data: pointer to place tag at
+ * @data_len: remaining size of @data buffer
+ * @tag: tag to be placed
+ * @string: the data to be tagged
+ * @len: the length of the data to be tagged
+ *
+ * Note this currently only handles short form tags < 31.  To encode
+ * in place pass a NULL @string and -1 for @len; all this will do is
+ * add an indefinite length tag and update the data pointer to the
+ * place where the tag contents should be placed.  After the data is
+ * placed, repeat the prior statement but now with the known length.
+ * In order to avoid having to keep both before and after pointers,
+ * the repeat expects to be called with @data pointing to where the
+ * first encode placed it.  For the recode case, set @data_len to NULL
+ */
+int asn1_encode_tag(unsigned char **data, int *data_len, u32 tag,
+		    const unsigned char *string, int len)
+{
+	int ret, dummy_len = 2;
+
+	if (WARN(tag > 30, "ASN.1 tag can't be > 30"))
+		return -EINVAL;
+
+	if (!string && WARN(len > 127,
+			    "BUG: recode tag is too big (>127)"))
+		return -EINVAL;
+
+	if (!string && len > 0) {
+		/*
+		 * we're recoding, so move back to the start of the
+		 * tag and install a dummy length because the real
+		 * data_len should be NULL
+		 */
+		*data -= 2;
+		data_len = &dummy_len;
+	}
+
+	if (*data_len < 2)
+		return -EINVAL;
+
+	*((*data)++) = _tagn(CONT, CONS, tag);
+	(*data_len)--;
+	ret = asn1_encode_length(data, data_len, len);
+	if (ret < 0)
+		return ret;
+	if (!string)
+		return 0;
+	if (*data_len < len)
+		return -EINVAL;
+	memcpy(*data, string, len);
+	*data += len;
+	*data_len -= len;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_tag);
+
+/**
+ * asn1_encode_octet_string - encode an ASN.1 OCTET STRING
+ * @data: pointer to encode at
+ * @data_len: bytes remaining in @data buffer
+ * @string: string to be encoded
+ * @len: length of string
+ *
+ * Note ASN.1 octet strings may contain zeros, so the length is obligatory.
+ */
+int asn1_encode_octet_string(unsigned char **data, int *data_len,
+			     const unsigned char *string, u32 len)
+{
+	int ret;
+
+	if (*data_len < 2)
+		return -EINVAL;
+
+	*((*data)++) = _tag(UNIV, PRIM, OTS);
+	(*data_len)--;
+	ret = asn1_encode_length(data, data_len, len);
+	if (ret)
+		return ret;
+
+	if (*data_len < len)
+		return -EINVAL;
+
+	memcpy(*data, string, len);
+	*data += len;
+	*data_len -= len;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_octet_string);
+
+/**
+ * asn1_encode_sequence - wrap a byte stream in an ASN.1 SEQUENCE
+ * @data: pointer to encode at
+ * @data_len: remaining size of @data pointer
+ * @seq: data to be encoded as a sequence
+ * @len: length of the data to be encoded as a sequence
+ *
+ * Fill in a sequence.  To encode in place, pass NULL for @seq and -1
+ * for @len; then call again once the length is known (still with NULL
+ * for @seq). In order to avoid having to keep both before and after
+ * pointers, the repeat expects to be called with @data pointing to
+ * where the first encode placed it.  The recode case should pass NULL
+ * to @data_size
+ */
+int asn1_encode_sequence(unsigned char **data, int *data_len,
+			 const unsigned char *seq, int len)
+{
+	int ret, dummy_len = 2;
+
+	if (!seq && WARN(len > 127,
+			 "BUG: recode sequence is too big (>127)"))
+		return -EINVAL;
+	if (!seq && len >= 0) {
+		/*
+		 * we're recoding, so move back to the start of the
+		 * sequence and install a dummy length because the
+		 * real length should be NULL
+		 */
+		*data -= 2;
+		data_len = &dummy_len;
+	}
+
+	if (*data_len < 2)
+		return -EINVAL;
+
+	*((*data)++) = _tag(UNIV, CONS, SEQ);
+	(*data_len)--;
+	ret = asn1_encode_length(data, data_len, len);
+	if (ret)
+		return ret;
+	if (!seq)
+		return 0;
+
+	if (*data_len < len)
+		return -EINVAL;
+
+	memcpy(*data, seq, len);
+	*data += len;
+	*data_len -= len;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_sequence);
+
+/**
+ * asn1_encode_boolean - encode a boolean value to ASN.1
+ * @data: pointer to encode at
+ * @data_len: bytes remaining in @data buffer
+ * @val: the boolean true/false value
+ */
+int asn1_encode_boolean(unsigned char **data, int *data_len, bool val)
+{
+	if (*data_len < 2)
+		return -EINVAL;
+	*((*data)++) = _tag(UNIV, PRIM, BOOL);
+	asn1_encode_length(data, data_len, 1);
+	(*data_len)--;
+	*((*data)++) = val ? 1 : 0;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_boolean);

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Tue, 2019-12-10 at 22:37 +0000, David Woodhouse wrote:
> 
> On 10 December 2019 18:53:40 GMT, James Bottomley <James.Bottomley@Ha
> nsenPartnership.com> wrote:
> > On Tue, 2019-12-10 at 14:08 +0000, David Howells wrote:
> > >   Please therefore put bounds checking and error handling in
> > > it.  And
> > > please *don't* just produce broken ASN.1 when something goes
> > > wrong.
> > 
> > OK, I'll make it return an error and add a wrapper for my use case
> > that
> > warns on error and causes the function to bail.
> 
> Traditionally we call that "error handling" :p

This is what I'm thinking (still reworking the rest of the series ... I
found out that AA doesn't habitually have power sockets and my laptop
dying in the middle of a rebase turned out not to be such a good
thing).

James

---

From 7b0c52cf07ca2b8b8ddbe0442a6d3f9de30f7b1b Mon Sep 17 00:00:00 2001
From: James Bottomley <James.Bottomley@HansenPartnership.com>
Date: Wed, 4 Dec 2019 15:19:01 -0800
Subject: [PATCH] lib: add asn.1 encoder

We have a need in the TPM trusted keys to return the ASN.1 form of the
TPM key blob so it can be operated on by tools outside of the kernel.
To do that, we have to be able to read and write the key format.  The
current ASN.1 decoder does fine for reading, but we need pieces of an
ASN.1 encoder to return the key blob.

The current implementation only encodes the ASN.1 bits we actually need.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

---

v2: updated API to use indefinite length, and made symbol exports gpl

diff --git a/include/linux/asn1_encoder.h b/include/linux/asn1_encoder.h
new file mode 100644
index 000000000000..f4afe5ad79a8
--- /dev/null
+++ b/include/linux/asn1_encoder.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _LINUX_ASN1_ENCODER_H
+#define _LINUX_ASN1_ENCODER_H
+
+#include <linux/types.h>
+#include <linux/asn1.h>
+#include <linux/asn1_ber_bytecode.h>
+#include <linux/bug.h>
+
+#define asn1_oid_len(oid) (sizeof(oid)/sizeof(u32))
+int asn1_encode_integer(unsigned char **_data, int *data_len,
+			s64 integer);
+int asn1_encode_oid(unsigned char **_data, int *data_len,
+		    u32 oid[], int oid_len);
+int asn1_encode_tag(unsigned char **data, int *data_len, u32 tag,
+		    const unsigned char *string, int len);
+int asn1_encode_octet_string(unsigned char **data, int *data_len,
+			     const unsigned char *string, u32 len);
+int asn1_encode_sequence(unsigned char **data, int *data_len,
+			 const unsigned char *seq, int len);
+int asn1_encode_boolean(unsigned char **data, int *data_len, bool val);
+
+#endif
diff --git a/lib/Makefile b/lib/Makefile
index c2f0e2a4e4e8..515b35f92c3c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -233,7 +233,7 @@ obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o
 
 obj-$(CONFIG_PERCPU_TEST) += percpu_test.o
 
-obj-$(CONFIG_ASN1) += asn1_decoder.o
+obj-$(CONFIG_ASN1) += asn1_decoder.o asn1_encoder.o
 
 obj-$(CONFIG_FONT_SUPPORT) += fonts/
 
diff --git a/lib/asn1_encoder.c b/lib/asn1_encoder.c
new file mode 100644
index 000000000000..c3c03bad7e6a
--- /dev/null
+++ b/lib/asn1_encoder.c
@@ -0,0 +1,362 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Simple encoder primitives for ASN.1 BER/DER/CER
+ *
+ * Copyright (C) 2019 James.Bottomley@HansenPartnership.com
+ */
+
+#include <linux/asn1_encoder.h>
+#include <linux/bug.h>
+#include <linux/string.h>
+#include <linux/module.h>
+
+/**
+ * asn1_encode_integer - encode positive integer to ASN.1
+ * @_data: pointer to the pointer to the data
+ * @data_len: length of buffer remaining
+ * @integer: integer to be encoded
+ *
+ * This is a simplified encoder: it only currently does
+ * positive integers, but it should be simple enough to add the
+ * negative case if a use comes along.
+ */
+int asn1_encode_integer(unsigned char **_data, int *data_len, s64 integer)
+{
+	unsigned char *data = *_data, *d = &data[2];
+	int i;
+	bool found = false;
+
+	if (WARN(integer < 0,
+		 "BUG: integer encode only supports positive integers"))
+		return -EINVAL;
+
+	if (*data_len < 3)
+		return -EINVAL;
+
+	*data_len -= 2;
+
+	data[0] = _tag(UNIV, PRIM, INT);
+	if (integer == 0) {
+		*d++ = 0;
+		goto out;
+	}
+	for (i = sizeof(integer); i > 0 ; i--) {
+		int byte = integer >> (8*(i-1));
+
+		if (!found && byte == 0)
+			continue;
+		found = true;
+		if (byte & 0x80) {
+			/*
+			 * no check needed here, we already know we
+			 * have len >= 1
+			 */
+			*d++ = 0;
+			(*data_len)--;
+		}
+		if (*data_len == 0)
+			return -EINVAL;
+		*d++ = byte;
+		(*data_len)--;
+	}
+ out:
+	data[1] = d - data - 2;
+	*_data = d;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_integer);
+
+/* calculate the base 128 digit values setting the top bit of the first octet */
+static int asn1_encode_oid_digit(unsigned char **_data, int *data_len, u32 oid)
+{
+	int start = 7 + 7 + 7 + 7;
+	unsigned char *data = *_data;
+	int ret = 0;
+
+	if (*data_len < 1)
+		return -EINVAL;
+
+	/* quick case */
+	if (oid == 0) {
+		*data++ = 0x80;
+		(*data_len)--;
+		goto out;
+	}
+
+	while (oid >> start == 0)
+		start -= 7;
+
+	while (start > 0 && *data_len > 0) {
+		u8 byte;
+
+		byte = oid >> start;
+		oid = oid - (byte << start);
+		start -= 7;
+		byte |= 0x80;
+		*data++ = byte;
+		(*data_len)--;
+	}
+	if (*data_len > 0) {
+		*data++ = oid;
+		(*data_len)--;
+	} else {
+		ret = -EINVAL;
+	}
+
+ out:
+	*_data = data;
+	return ret;
+}
+
+/**
+ * asn1_encode_oid - encode an oid to ASN.1
+ * @_data: position to begin encoding at
+ * @data_len: remaining bytes in @_data
+ * @oid: array of oids
+ * @oid_len: length of oid array
+ *
+ * this encodes an OID up to ASN.1 when presented as an array of OID values
+ */
+int asn1_encode_oid(unsigned char **_data, int *data_len,
+		    u32 oid[], int oid_len)
+{
+	unsigned char *data = *_data;
+	unsigned char *d = data + 2;
+	int i, ret;
+
+	if (WARN(oid_len < 2, "OID must have at least two elements"))
+		return -EINVAL;
+	if (WARN(oid_len > 32, "OID is too large"))
+		return -EINVAL;
+	if (*data_len < 2)
+		return -EINVAL;
+
+	data[0] = _tag(UNIV, PRIM, OID);
+	*d++ = oid[0] * 40 + oid[1];
+	*data_len -= 2;
+	ret = 0;
+	for (i = 2; i < oid_len; i++) {
+		ret = asn1_encode_oid_digit(&d, data_len, oid[i]);
+		if (ret < 0)
+			return ret;
+	}
+	data[1] = d - data - 2;
+	*_data = d;
+	return ret;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_oid);
+
+static int asn1_encode_length(unsigned char **data, int *data_len, int len)
+{
+	if (*data_len < 1)
+		return -EINVAL;
+	(*data_len)--;
+	if (len < 0) {
+		*((*data)++) = ASN1_INDEFINITE_LENGTH;
+		return 0;
+	}
+	if (*data_len < 1)
+		return -EINVAL;
+	if (len <= 0x7f) {
+		*((*data)++) = len;
+		(*data_len)--;
+		return 0;
+	}
+
+	if (*data_len < 2)
+		return -EINVAL;
+	if (len <= 0xff) {
+		*((*data)++) = 0x81;
+		*((*data)++) = len & 0xff;
+		*data_len -= 2;
+		return 0;
+	}
+	if (*data_len < 3)
+		return -EINVAL;
+	if (len <= 0xffff) {
+		*((*data)++) = 0x82;
+		*((*data)++) = (len >> 8) & 0xff;
+		*((*data)++) = len & 0xff;
+		*data_len -= 3;
+		return 0;
+	}
+
+	if (WARN(len > 0xffffff, "ASN.1 length can't be > 0xffffff"))
+		return -EINVAL;
+
+	if (*data_len < 4)
+		return -EINVAL;
+	*((*data)++) = 0x83;
+	*((*data)++) = (len >> 16) & 0xff;
+	*((*data)++) = (len >> 8) & 0xff;
+	*((*data)++) = len & 0xff;
+	*data_len -= 4;
+
+	return 0;
+}
+
+/**
+ * asn1_encode_tag - add a tag for optional or explicit value
+ * @data: pointer to place tag at
+ * @data_len: remaining size of @data buffer
+ * @tag: tag to be placed
+ * @string: the data to be tagged
+ * @len: the length of the data to be tagged
+ *
+ * Note this currently only handles short form tags < 31.  To encode
+ * in place pass a NULL @string and -1 for @len; all this will do is
+ * add an indefinite length tag and update the data pointer to the
+ * place where the tag contents should be placed.  After the data is
+ * placed, repeat the prior statement but now with the known length.
+ * In order to avoid having to keep both before and after pointers,
+ * the repeat expects to be called with @data pointing to where the
+ * first encode placed it.  For the recode case, set @data_len to NULL
+ */
+int asn1_encode_tag(unsigned char **data, int *data_len, u32 tag,
+		    const unsigned char *string, int len)
+{
+	int ret, dummy_len = 2;
+
+	if (WARN(tag > 30, "ASN.1 tag can't be > 30"))
+		return -EINVAL;
+
+	if (!string && WARN(len > 127,
+			    "BUG: recode tag is too big (>127)"))
+		return -EINVAL;
+
+	if (!string && len > 0) {
+		/*
+		 * we're recoding, so move back to the start of the
+		 * tag and install a dummy length because the real
+		 * data_len should be NULL
+		 */
+		*data -= 2;
+		data_len = &dummy_len;
+	}
+
+	if (*data_len < 2)
+		return -EINVAL;
+
+	*((*data)++) = _tagn(CONT, CONS, tag);
+	(*data_len)--;
+	ret = asn1_encode_length(data, data_len, len);
+	if (ret < 0)
+		return ret;
+	if (!string)
+		return 0;
+	if (*data_len < len)
+		return -EINVAL;
+	memcpy(*data, string, len);
+	*data += len;
+	*data_len -= len;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_tag);
+
+/**
+ * asn1_encode_octet_string - encode an ASN.1 OCTET STRING
+ * @data: pointer to encode at
+ * @data_len: bytes remaining in @data buffer
+ * @string: string to be encoded
+ * @len: length of string
+ *
+ * Note ASN.1 octet strings may contain zeros, so the length is obligatory.
+ */
+int asn1_encode_octet_string(unsigned char **data, int *data_len,
+			     const unsigned char *string, u32 len)
+{
+	int ret;
+
+	if (*data_len < 2)
+		return -EINVAL;
+
+	*((*data)++) = _tag(UNIV, PRIM, OTS);
+	(*data_len)--;
+	ret = asn1_encode_length(data, data_len, len);
+	if (ret)
+		return ret;
+
+	if (*data_len < len)
+		return -EINVAL;
+
+	memcpy(*data, string, len);
+	*data += len;
+	*data_len -= len;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_octet_string);
+
+/**
+ * asn1_encode_sequence - wrap a byte stream in an ASN.1 SEQUENCE
+ * @data: pointer to encode at
+ * @data_len: remaining size of @data pointer
+ * @seq: data to be encoded as a sequence
+ * @len: length of the data to be encoded as a sequence
+ *
+ * Fill in a sequence.  To encode in place, pass NULL for @seq and -1
+ * for @len; then call again once the length is known (still with NULL
+ * for @seq). In order to avoid having to keep both before and after
+ * pointers, the repeat expects to be called with @data pointing to
+ * where the first encode placed it.  The recode case should pass NULL
+ * to @data_size
+ */
+int asn1_encode_sequence(unsigned char **data, int *data_len,
+			 const unsigned char *seq, int len)
+{
+	int ret, dummy_len = 2;
+
+	if (!seq && WARN(len > 127,
+			 "BUG: recode sequence is too big (>127)"))
+		return -EINVAL;
+	if (!seq && len >= 0) {
+		/*
+		 * we're recoding, so move back to the start of the
+		 * sequence and install a dummy length because the
+		 * real length should be NULL
+		 */
+		*data -= 2;
+		data_len = &dummy_len;
+	}
+
+	if (*data_len < 2)
+		return -EINVAL;
+
+	*((*data)++) = _tag(UNIV, CONS, SEQ);
+	(*data_len)--;
+	ret = asn1_encode_length(data, data_len, len);
+	if (ret)
+		return ret;
+	if (!seq)
+		return 0;
+
+	if (*data_len < len)
+		return -EINVAL;
+
+	memcpy(*data, seq, len);
+	*data += len;
+	*data_len -= len;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_sequence);
+
+/**
+ * asn1_encode_boolean - encode a boolean value to ASN.1
+ * @data: pointer to encode at
+ * @data_len: bytes remaining in @data buffer
+ * @val: the boolean true/false value
+ */
+int asn1_encode_boolean(unsigned char **data, int *data_len, bool val)
+{
+	if (*data_len < 2)
+		return -EINVAL;
+	*((*data)++) = _tag(UNIV, PRIM, BOOL);
+	asn1_encode_length(data, data_len, 1);
+	(*data_len)--;
+	*((*data)++) = val ? 1 : 0;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_boolean);

Re: [PATCH v2 0/8] Fix TPM 2.0 trusted keys

[Jarkko Sakkinen]

On Mon, Dec 09, 2019 at 04:04:32PM -0800, James Bottomley wrote:
> This fixes a wide array of problems with the current TPM 2.0
> implementation of trusted keys.  Since policy based trusted keys never
> worked in the current implementation, I've rewritten the policy
> implementation to make it easier to use and so the trusted key handler
> can understand what elements of a policy are failing and why.
> 
> Apart from fixing bugs like volatile object leakage, I've changed the
> output format to use the standardised ASN.1 coding for TPM2 keys,
> meaning they should interoperate with userspace TPM2 key
> implementations.  Apart from interoperability, another advantage of the
> existing key format is that it carries all parameters like parent and
> hash with it and it is capable of carrying policy directives in a way
> that mean they're tied permanently to the key (no having to try to
> remember what the policy was and reconstruct it from userspace).  This
> actually allows us to support the TPM 1.2 commands like pcrinfo easily
> in 2.0.
> 
> The big problem with this patch is still that we can't yet combine
> policy with authorization because that requires proper session
> handling, but at least with this rewrite it becomes possible (whereas
> it was never possible with the old external policy session code). 
> Thus, when we have the TPM 2.0 security patch upstream, we'll be able
> to use the session logic from that patch to imlement authorizations.

Testing as soon as we have more urgent issues out of the table.

/Jarkko

Re: [PATCH v2 0/8] Fix TPM 2.0 trusted keys

[Jarkko Sakkinen]

On Mon, Dec 09, 2019 at 04:04:32PM -0800, James Bottomley wrote:
> This fixes a wide array of problems with the current TPM 2.0
> implementation of trusted keys.  Since policy based trusted keys never
> worked in the current implementation, I've rewritten the policy
> implementation to make it easier to use and so the trusted key handler
> can understand what elements of a policy are failing and why.
> 
> Apart from fixing bugs like volatile object leakage, I've changed the
> output format to use the standardised ASN.1 coding for TPM2 keys,
> meaning they should interoperate with userspace TPM2 key
> implementations.  Apart from interoperability, another advantage of the
> existing key format is that it carries all parameters like parent and
> hash with it and it is capable of carrying policy directives in a way
> that mean they're tied permanently to the key (no having to try to
> remember what the policy was and reconstruct it from userspace).  This
> actually allows us to support the TPM 1.2 commands like pcrinfo easily
> in 2.0.
> 
> The big problem with this patch is still that we can't yet combine
> policy with authorization because that requires proper session
> handling, but at least with this rewrite it becomes possible (whereas
> it was never possible with the old external policy session code). 
> Thus, when we have the TPM 2.0 security patch upstream, we'll be able
> to use the session logic from that patch to imlement authorizations.

Testing as soon as we have more urgent issues out of the table.

/Jarkko

Re: [PATCH v2 0/8] Fix TPM 2.0 trusted keys

[James Bottomley]

On Mon, 2019-12-09 at 16:04 -0800, James Bottomley wrote:
[...]
> The big problem with this patch is still that we can't yet combine
> policy with authorization because that requires proper session
> handling, but at least with this rewrite it becomes possible (whereas
> it was never possible with the old external policy session code). 
> Thus, when we have the TPM 2.0 security patch upstream, we'll be able
> to use the session logic from that patch to imlement authorizations.

I had a discussion with Ken Goldman on Friday where he told me this
wasn't true: we can actually persuade a policy session to do a non-HMAC 
authorization (for the interested, the trick is to use
TPM2_PolicyPassword in place of TPM2_PolicyAuthValue.  It hashes to the
same policy but the former sets the session up for non-HMAC and the
latter for HMAC) so I'll add password based authorization to policies
when I respin the patch set.

James

Re: [PATCH v2 0/8] Fix TPM 2.0 trusted keys

[James Bottomley]

On Mon, 2019-12-09 at 16:04 -0800, James Bottomley wrote:
[...]
> The big problem with this patch is still that we can't yet combine
> policy with authorization because that requires proper session
> handling, but at least with this rewrite it becomes possible (whereas
> it was never possible with the old external policy session code). 
> Thus, when we have the TPM 2.0 security patch upstream, we'll be able
> to use the session logic from that patch to imlement authorizations.

I had a discussion with Ken Goldman on Friday where he told me this
wasn't true: we can actually persuade a policy session to do a non-HMAC 
authorization (for the interested, the trick is to use
TPM2_PolicyPassword in place of TPM2_PolicyAuthValue.  It hashes to the
same policy but the former sets the session up for non-HMAC and the
latter for HMAC) so I'll add password based authorization to policies
when I respin the patch set.

James

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[David Howells]

James Bottomley <James.Bottomley@HansenPartnership.com> wrote:

> +/**
> + * asn1_encode_octet_string - encode an ASN.1 OCTET STRING
> + * @data: pointer to encode at
> + * @data_len: bytes remaining in @data buffer
> + * @string: string to be encoded
> + * @len: length of string
> + *
> + * Note ASN.1 octet strings may contain zeros, so the length is obligatory.
> + */
> +int asn1_encode_octet_string(unsigned char **data, int *data_len,
> +			     const unsigned char *string, u32 len)

I wonder if it makes more sense to pass in an end pointer and return the new
data pointer (or an error), ie.:

unsigned char *asn1_encode_octet_string(unsigned char *data,
				        unsigned char *data_end,
					const unsigned char *string, u32 len)

Further, I wonder - does it actually make more sense to encode backwards,
ie. start at the end of the buffer and do the last element first, working
towards the front.

The disadvantage being that the data start would likely not be coincident with
the buffer start.

David

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Wed, 2019-12-18 at 10:50 +0000, David Howells wrote:
> James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> 
> > +/**
> > + * asn1_encode_octet_string - encode an ASN.1 OCTET STRING
> > + * @data: pointer to encode at
> > + * @data_len: bytes remaining in @data buffer
> > + * @string: string to be encoded
> > + * @len: length of string
> > + *
> > + * Note ASN.1 octet strings may contain zeros, so the length is
> > obligatory.
> > + */
> > +int asn1_encode_octet_string(unsigned char **data, int *data_len,
> > +			     const unsigned char *string, u32 len)
> 
> I wonder if it makes more sense to pass in an end pointer and return
> the new data pointer (or an error), ie.:
> 
> unsigned char *asn1_encode_octet_string(unsigned char *data,
> 				        unsigned char *data_end,
> 					const unsigned char *string,
> u32 len)

On the first point: people are prone to get off by one confusion on
data_end pointers (should they point to the last byte in the buffer or
one beyond).  If I look at how I use the API, I've no real use for
either length remaining or the end pointer, so I think it makes no
difference to the consumer, it's just stuff you have to do for the API.
 If I look at the internal API use, we definitely need the length
remaining, so I've a marginal preference for that format, but since
it's easy to work out it is very marginal.

> Further, I wonder - does it actually make more sense to encode
> backwards, ie. start at the end of the buffer and do the last element
> first, working towards the front.

Heh, let me ask you this: do you use a reverse polish notation
calculator ... The problem is that it makes the ASN.1 hard to construct
 for the API user and hard to read for the reviewer because of the
order reversal.  Debugging is going to be a pain because you're going
to get the output of asn1parse and have to read it backwards to see
where the problems are.

> The disadvantage being that the data start would likely not be
> coincident with the buffer start.

This would be a big issue: in several routines I allocate a buffer,
fill it with ASN.1 and pass it back and the receiving routine has to
free it.  Now the buffer won't be freeable by the pointer I pass back
because that may not be where the allocation was done.

For these two reasons, I'd like to keep the work forwards behaviour. 
I'm reasonably ambivalent on the end pointer with a marginal preference
for passing in the length remaining instead.

James

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Wed, 2019-12-18 at 10:50 +0000, David Howells wrote:
> James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> 
> > +/**
> > + * asn1_encode_octet_string - encode an ASN.1 OCTET STRING
> > + * @data: pointer to encode at
> > + * @data_len: bytes remaining in @data buffer
> > + * @string: string to be encoded
> > + * @len: length of string
> > + *
> > + * Note ASN.1 octet strings may contain zeros, so the length is
> > obligatory.
> > + */
> > +int asn1_encode_octet_string(unsigned char **data, int *data_len,
> > +			     const unsigned char *string, u32 len)
> 
> I wonder if it makes more sense to pass in an end pointer and return
> the new data pointer (or an error), ie.:
> 
> unsigned char *asn1_encode_octet_string(unsigned char *data,
> 				        unsigned char *data_end,
> 					const unsigned char *string,
> u32 len)

On the first point: people are prone to get off by one confusion on
data_end pointers (should they point to the last byte in the buffer or
one beyond).  If I look at how I use the API, I've no real use for
either length remaining or the end pointer, so I think it makes no
difference to the consumer, it's just stuff you have to do for the API.
 If I look at the internal API use, we definitely need the length
remaining, so I've a marginal preference for that format, but since
it's easy to work out it is very marginal.

> Further, I wonder - does it actually make more sense to encode
> backwards, ie. start at the end of the buffer and do the last element
> first, working towards the front.

Heh, let me ask you this: do you use a reverse polish notation
calculator ... The problem is that it makes the ASN.1 hard to construct
 for the API user and hard to read for the reviewer because of the
order reversal.  Debugging is going to be a pain because you're going
to get the output of asn1parse and have to read it backwards to see
where the problems are.

> The disadvantage being that the data start would likely not be
> coincident with the buffer start.

This would be a big issue: in several routines I allocate a buffer,
fill it with ASN.1 and pass it back and the receiving routine has to
free it.  Now the buffer won't be freeable by the pointer I pass back
because that may not be where the allocation was done.

For these two reasons, I'd like to keep the work forwards behaviour. 
I'm reasonably ambivalent on the end pointer with a marginal preference
for passing in the length remaining instead.

James

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Thu, 2019-12-19 at 08:10 +0900, James Bottomley wrote:
> On Wed, 2019-12-18 at 10:50 +0000, David Howells wrote:
> > James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> > 
> > > +/**
> > > + * asn1_encode_octet_string - encode an ASN.1 OCTET STRING
> > > + * @data: pointer to encode at
> > > + * @data_len: bytes remaining in @data buffer
> > > + * @string: string to be encoded
> > > + * @len: length of string
> > > + *
> > > + * Note ASN.1 octet strings may contain zeros, so the length is
> > > obligatory.
> > > + */
> > > +int asn1_encode_octet_string(unsigned char **data, int
> > > *data_len,
> > > +			     const unsigned char *string, u32
> > > len)
> > 
> > I wonder if it makes more sense to pass in an end pointer and
> > return
> > the new data pointer (or an error), ie.:
> > 
> > unsigned char *asn1_encode_octet_string(unsigned char *data,
> > 				        unsigned char *data_end,
> > 					const unsigned char *string,
> > u32 len)
> 
> On the first point: people are prone to get off by one confusion on
> data_end pointers (should they point to the last byte in the buffer
> or
> one beyond).  If I look at how I use the API, I've no real use for
> either length remaining or the end pointer, so I think it makes no
> difference to the consumer, it's just stuff you have to do for the
> API.
>  If I look at the internal API use, we definitely need the length
> remaining, so I've a marginal preference for that format, but since
> it's easy to work out it is very marginal.
> 
> > Further, I wonder - does it actually make more sense to encode
> > backwards, ie. start at the end of the buffer and do the last
> > element
> > first, working towards the front.
> 
> Heh, let me ask you this: do you use a reverse polish notation
> calculator ... The problem is that it makes the ASN.1 hard to
> construct  for the API user and hard to read for the reviewer because
> of the order reversal.  Debugging is going to be a pain because
> you're going to get the output of asn1parse and have to read it
> backwards to see where the problems are.

I coded this up to see what it would look like, and I think it can all
be made to work with error pass through.  The latter is because you
want to build up sequences of

data = asn1_encode...(data, ...);
data = asn1_encode...(data, ...);
data = asn1_encode...(data, ...);

And only check for errors when you're finished.  I think the interface
looks nicer than a modifying pointer, so if you wait for the v4 patches
they'll show this new interface with the consumers.

James

Re: [PATCH v2 2/8] lib: add asn.1 encoder

[James Bottomley]

On Thu, 2019-12-19 at 08:10 +0900, James Bottomley wrote:
> On Wed, 2019-12-18 at 10:50 +0000, David Howells wrote:
> > James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> > 
> > > +/**
> > > + * asn1_encode_octet_string - encode an ASN.1 OCTET STRING
> > > + * @data: pointer to encode at
> > > + * @data_len: bytes remaining in @data buffer
> > > + * @string: string to be encoded
> > > + * @len: length of string
> > > + *
> > > + * Note ASN.1 octet strings may contain zeros, so the length is
> > > obligatory.
> > > + */
> > > +int asn1_encode_octet_string(unsigned char **data, int
> > > *data_len,
> > > +			     const unsigned char *string, u32
> > > len)
> > 
> > I wonder if it makes more sense to pass in an end pointer and
> > return
> > the new data pointer (or an error), ie.:
> > 
> > unsigned char *asn1_encode_octet_string(unsigned char *data,
> > 				        unsigned char *data_end,
> > 					const unsigned char *string,
> > u32 len)
> 
> On the first point: people are prone to get off by one confusion on
> data_end pointers (should they point to the last byte in the buffer
> or
> one beyond).  If I look at how I use the API, I've no real use for
> either length remaining or the end pointer, so I think it makes no
> difference to the consumer, it's just stuff you have to do for the
> API.
>  If I look at the internal API use, we definitely need the length
> remaining, so I've a marginal preference for that format, but since
> it's easy to work out it is very marginal.
> 
> > Further, I wonder - does it actually make more sense to encode
> > backwards, ie. start at the end of the buffer and do the last
> > element
> > first, working towards the front.
> 
> Heh, let me ask you this: do you use a reverse polish notation
> calculator ... The problem is that it makes the ASN.1 hard to
> construct  for the API user and hard to read for the reviewer because
> of the order reversal.  Debugging is going to be a pain because
> you're going to get the output of asn1parse and have to read it
> backwards to see where the problems are.

I coded this up to see what it would look like, and I think it can all
be made to work with error pass through.  The latter is because you
want to build up sequences of

data = asn1_encode...(data, ...);
data = asn1_encode...(data, ...);
data = asn1_encode...(data, ...);

And only check for errors when you're finished.  I think the interface
looks nicer than a modifying pointer, so if you wait for the v4 patches
they'll show this new interface with the consumers.

James